Congratulations!! and what a lucky little boy he is to be with such a caring family who will always hold him close to their hearts and home.
You are doing all the right things Hon, a careful introduction with little ones is important. I do this here with any breed, and you are spot on.
Staffy's are the best fence jumpers/scalers! they are such a loyal and devoted breed they insist on being with their people, and this will be more intense as a rescue babe. (the newbies will not leave me alone for weeks!)
I would suggest bringing him inside if you are out and about to be sure, particularly during the settling in period.
I agree feeding can be tricky during the settling in period. A small amount of good quality dry with a fresh raw diet is what i would recommend personally, some scraps and veges mixed through are loved as well, though any cooked bones are a disaster waiting to happen.
Give him some time to settle and before you know it he will be as fat as a fool believe me!
Oh, remove his bowl after 10/15 minutes to develop a routine and some feeding boundries. It is VERY hard to do with a new family member, but worth the effort...a bit like the toddler thing!