I think it's probable that James P was the son of George and one of the younger males in George's 1830 household. I recently downloaded George's estate docs but am still sorting through them, it's almost 150 pages. I'll let you know if there's any new info from that source.
Wonder why Arthur Newman was only becoming guardian in 1846, and who the guardian was before.
I don't recall whether I checked Dooly county for Canzada's marriages - I may have, I think I looked pretty much anywhere they could have occurred, regardless of how unlikely. I've run across the Pulaski county marriage record problem more than once. Canzada's marriage to James P. Cherry about 1836; Canzada's marriage to Arthur Newman about 1840; Edward Newman's marriage to Unknown about 1835; Catherine Newman to WG Hunt about 1859. All of these most likely did take place in Pulaski but the way the first four marriage books overlap - 1810-1851, 1840-1856, 1855-1869 and 1867-1876 - at least looks haphazard so it wouldn't surprise me to learn that some marriages never actually got recorded.
Another marriage record I didn't find was Arthur's daughter Sarah Jane to David F Matthews, which took place in Pulaski in 1865 according to her widows pension application.