Just found your post...thanks for posting all the info. I have an old photo of Richard Ellis Potter and his wife Rosa May Gallagher that Richard gave to his sister Nancy Marilda Potter. Nancy married James Lycurgas Coldiron -- Nancy was my great grandmother on my mother's side.
I have marriage date for John William Potter to the "Widow Fambrough" (Samantha) as: 19 Nov 1884 in Coryell, Texas. Not sure if source was reliable or not, as I haven't verified it.
I'd be happy to correspond with you so we can share info.