Casey, Since my last post in January I have found some new (for me) info which may be interesting for you too.
I have found an 1830 census record for Philip Dufford in Luzerne Co., Newport Twp., which is definitely Philip Jr.. Also in this census (as in 1840 and 1850), there is an older woman in the household, who is named Elisabeth Dufford in the 1850 census. This suggests that her husband (who you say was also a Philip) died before 1830, and not around 1845.
I have browsed the same township in 1820 and found absolutely nothing that looks like a Dufford -- but did find the family of my Philip Dufford's wife (Elisabeth Gruver)living in that township: Michael Gruver.
The 1840 Butler census-- Philip Dufford-- image first lists an older man, but this mark has been erased and is not counted in the subtotal at the bottom of the image, supporting the 1830 census.
This all would seem to prove that my Philip's mother was Elisabeth-something, but I haven't been able to prove the Philip Sr. name yet. Do you have a reference for that? Quite confusing, 2 Philips married to 2 Elisabeths!
Also, in the 1830 census, Philip, then 20, also has a young boy in his house, aged 5 - 10 (son or otherwise). This child is also in the 1840 census, but disappears in the 1850 census where there are 4 children named. I couldn't find a Dufford in Butler Co matching this age, but who knows.