He's very good looking! Although I don't think he's 100% CC. (Muzzel) is too long. However, first of all, I commend you for fostering him! People look to the breeders first for dogs not knowing (or choosing to be ignorant) of all the wonderful dogs avaliable at the shelters deserving of a loving environment. With that being said, it's unknown of the poor guys history. Was he abused?, mutiple dog houshould? neglected? etc...The main thing i'd suggest is patience. I'll share this with you. I adopted my cane 6 months ago (2 yr old nutered male)and brought him into a home with two Labs and two indoor cats. The shelter trainer said that he may be a little "edgy" with the other dogs and didn't think he'd do well with our cats because his prey-drive was a little high. My son is 23 yrs old and while trying to lay on him to pet him (like's he's always done with our labs) our Cane "Bear" growled at him. Now, I don't condone this, and after verbal correction it was fine. However, this happened within the first week. The dog was in a strange environment, with a new pack etc... Also he suffered from sever self-confidance issues. I am now happy to report that using patience and "finding" his way within the pack helped him to be the most sound dog I have now! And he and my cats sleep togeather! My labs also helped him to adjust and I think this was a huge key element also. Sounds like your pitts may be able to assist you in this regard as well.
Good luck to you.