Dewald and Dewalt are not nicknames, they are Anglicized spellings (and thus equivalents) of the German given name, Theobald (just as William is an Anglicized spelling of Wilhelm).

1.  Marriage Record:

2a.  Church Record of the Towamensing Union Church in Monroe County, Pa. [really Carbon Co., near Palmerton] (online at the Schoeler Genealogy web site):

Parents	Child & Dates	Sponsors
Dewald Straub Margaretha	Daniel 25 Apr 1801 27 May 1801	Daniel Brandstatter Christina
Theobald Straub Margaretha	David  1 Nov 1802 12 Dec 1802	Henrich Bloos Maira Luisa
Daniel Brandstätter	Johannes  6 Aug 1804 29 Aug 1804	Thebald Straus Marg. Blaas
Theobald Starup Margaret	Johannes 12 Jul 1807 16 Aug 1807	Georg Olwein Susanna
Martin Hausknecht Magdelene	Thomas 20 Feb 1808 27 Mar 1808	Theobald Straup Margarete
William Kehrn Esq. Johanne	Salome Anne  8 Dec 1808 26 May 1809	Theobald Straup Margarete
Dewald Straub Margaretha	Thomas 13 Feb 1809  1 Jun 1810	Peter Scneider Katharina Blos
Christina Straup Regina	Rebecca 17 Jul 1809 13 Aug 1809	Theobald Straup Margarete
John Dreisbach Elisabeth	Willhelm 27 Mar 1825 22 May 1825	Dewald Stroup Margaret
Daniel Bloss Elisabeth	Ruben 24 Jan 1828 16 Mar 1828	Theobald Straub Margarethe
Johan Straub Dorothy	Benjamin   8 Mar 1829  9 May 1829	Teobald Straub Margareth
David Straub Maria	Levi 18 May 1829 28 Jun 1829	Theobald Straub Margareth
James Bellford Anna	Henryette 19 Mar 1834  4 Apr 1834	Dewalt Straub Margarethe

2b.  Church Records: Adams, Berks & Lancaster Counties, Pennsylvania, 1729-1881 (Broderbund CD-129):

Record ID: 280378 Location: Berks Co., PA Church: Christ Church on Bieber Creek or Mertz Church, Rockland [Twp.] Elisabeth Angstadt Birth: Jun 15, 1796; Baptism: Nov 13, 1796 Father: Peter Angstadt; Mother: Maria Angstadt Sponsors: Dewald Straub and Christina Maertzin

Dewaldt appears to be unmarried at this point because no wife is mentioned.  (Christian STRAUB's daughter married a BIEBER/BEABER.) 

2c.  Church Records:  Selected Areas of Pennsylvania, 1600s-1800s (Broderbund CD-166):  same record as above (on CD-129).

3.  1800 Census Index and Digital Images (online at Ancestry.com; Image #57 of 66; extracted by Diana Gale Matthiesen):¤•

1800

PA

Northampton [now Carbon] Co.

Towamensing Twp.

p. 630

Ln. 12

Dewalt Straub

00100-00100-00

These data indicate:

No. & Sex	Age Class	Therefore Born	Individuals Inferred
1 male	16-25	1774-1784	= Dewaldt
1 female	16-25	1774-1784	= Wife

Dewaldt and his wife appear to be young newlyweds.  List is (roughly) alphabetical, so no neighborhood reconstruction is possible.  Dewalt is the only STRAUB/etc. in Carbon County.

4.  1810 Census Index and Digital Images (online at Ancestry.com; Image #1 of 1; extracted by Diana Gale Matthiesen):¤•

1810

PA

Northampton [now Carbon] Co.

Towamensing Twp.

p. 76A/87/94

Ln. 43

Dewald Stroup

41100-00010-00

These data indicate:

No. & Sex	Age Class	Therefore Born	Individuals Inferred
4 males	9 or under	1800-1810	= Thomas (b. 1809) = Johannes (b. 1807) = David (b. 1802) = Daniel (b. 1801)
1 male	10-15	1794-1800	= ?
1 male	16-25	1784-1794	=
0 males	26-44	1765-1784	= Theobald
1 female	26-44	1765-1784	= Margaret

There were no children in the household in the 1800 census, so the teenager appears not to be their child, unless he's in the wrong age class (or unless the 1800 census is wrong).  Theobald appears to be in the wrong age class.  The only other STRAUB in the township is Christian STRAUB. 

5.  1820 Census Index and Digital Images (online at Ancestry.com):  not found, and I searched every line of Towamensing Township.  I couldn't find Christian STRAUB or Daniel STRAUB, either, meaning whatever page they were on was lost or the enumerator missed that part of the county.

6.  1830 Census Index and Digital Images (online at Ancestry.com; Image #15 of 16; extracted by Diana Gale Matthiesen):¤•

1830

PA

Northampton [now Carbon] Co.

Towamensing Twp.

p. 214

Ln. 4

Dawalt Straub

000 110 001 - 101 100 100

These data indicate:

No. & Sex	Age Class	Therefore Born	Individuals Inferred
1 male	15-19	1810-1815	= Emanuel (b. 1814/5)
1 male	20-29	1800-1810	= Thomas (b. 1809)
1 male	60-69	1760-1770	= Theobald
1 female	4 or under	1825-1830	= Salinda (b. 1827)
1 female	10-14	1815-1820	= Rebecca (b. 1817)
1 female	15-19	1810-1815	= Anna (b. 1812)
1 female	40-49	1780-1790	= Margaret

Sons David and Johannes are enumerated as heads-of household, so the son still at home must be Thomas.  Dewaldt appears to be in the wrong age class, again, but in the other direction.

7.  1840 Census Index and Digital Images (online at Ancestry.com; Image #1-2 of 28; extracted by Diana Gale Matthiesen):¤•

1840

PA

Northampton Co.

Lehigh Twp.

pp. 164B-165A

Ln. 4

Dewald Straub

000 000 001 - 001 000 010

0001000

These data indicate:

No. & Sex	Age Class	Therefore Born	Individuals Inferred
1 male	60-69	1770-1780	= Theobald
1 female	10-14	1825-1830	= Salinda (b. 1827)
1 female	50-59	1780-1790	= Margaret
1	person engaged in manufactures and trades

Lehigh Twp., Carbon Co., was not created until 1875; this Lehigh Twp. really is in Northampton County. Christian STRAUB is in Allen Twp.  They are the only STRAUBs in Northampton Co. 

8.  1850 Census Every-Name-Index/Images (online at Ancestry.com):  not found.

9.  John W. Jordan, Edgar Moore Green, & George T. Ettinger, eds.  1905.  Historic Homes and Institutions and Genealogical and Personal Memoirs of the Lehigh Valley, Pennsylvania.  Lewis Publ. Co., New York (excerpts online at Karen Smith Furst's web site):

DAVID H. STRAUB, who is now living retired in Lehighton, but who for many years was industriously and successfully identified with agricultural pursuits in Carbon county, belongs to of the early families of the Lehigh Valley, of Than origin. His grandfather, Theodore Straub, was born in what is known as Dry Land, a little hamlet located between Easton and Bethlehem.  He was an extensive distiller, and a man of considerable force of character and local influence in his day, being widely known as an industrious, upright and worthy citizen.  His family numbered five sons:  Emanuel, Daniel, John, David and Thomas, and three daughters. David Straub, the father of D. H. Straub, was born at Dry Land...

What does "Than" mean?

10.  Archives of the STRAUB-L Mailing List (online at RootsWeb.com), including an informative post partially excerpted here:

...Dewalt STRAUB is... also listed as Theobald in some records.  The earliest record that I can find for Dewalt is November 13, 1796, where he is listed as a sponsor for the baptism of Elizabeth ANGSTADT, daughter of Peter & Maria ANGSTADT at Christ Church on Bieber Creek, Berks County... Dewalt died in 1844, intestate.  He was living in Towamensing Twp at the time of his death.  His probate records list his widow Margaretha and their eight children: Daniel, David, John, Thomas, Emanuel, Ann the wife of Charles Belford, Rebecca the wife of Thomas Brown, and Salinda, who at that time was still a minor.  The only other information I have on Dewalt is that he was issued a land warrant on November 6, 1833 for 25 acres in Northampton County... I've been told (but not able to prove as of yet) that Dewalt's wife Margaret BLOSE is the daughter of Henry BLOSE and the Granddaughter of Conrad BLOSE, who fought in the Revolutionary War and died at the Battle of Long Island.  At the same time that Dewalt and Margaret christened their four children at St. John's Luthern Church there was a couple by the name of Christian and Regina STRAUP who christened three children.  Their children were Carl (B 8-30-1805), Magdalene (B 6-13-1807), and Rebecca (B 7-17-1809).  Dewalt and Margaret were the sponsers for Rebecca.  Because of this I believe that Dewalt and Christian are somehow related.  I don't believe that this Christian is the son of Valentin and Elizabeth STRAUB.  Their Christian is listed as being born 8-22-1791, which would make him 14 years old at the time Carl was born in 1805...