Most of this info you probably have, but doesn't hurt to post for others.
1830/40 Warrick Co is Young J [John] KARR [prob b c 1810] with family.Married 7-29-1829 Polly BAKER, Warrick Co IN. Perhaps this is Rob't's bro??? 12-13-1828 Nancy KARR m Daniel MORGAN, Warrick Co
Oftentimes we have to track down family members to obtain info.Have you checked Spencer/Warrick Cos for early probate records for KARR/CARR?
It was customary for weddings to take place in the home of the bride, so Tabitha probably lived Spencer Co, with Rob't possibly living elsewhere, Warrick Co maybe????
Robt named his son John.I would imagine this is also the name of his father. 1st dau was Elizabeth.Long shot, but maybe this is a possibility.... http://familysearch.org/pal:/MM9.1.1/F477-PVHhttp://familysearch.org/pal:/MM9.1.1/F477-PVH
Robt's murder trial was Oct term 1839...change of venue to Gibson Co IN.
10-25-1841 Thomas LANG m. Tabitha CARR, Spencer Co IN
I gave up after 25yrs on several lines after finding nothing new.Sometimes it's just time to call it a day.