I wouldn't change his food just yet, but definitely start to look for good quality brands (if he isn't already eating something good). Same with treats, get good healthy stuff. (NO GREENIES and NO RAW HIDES or PIGS EARS) they are dangerous - Bully Sticks are good
Make sure you get him neutered (if he isn't already). And at age 2 - he shouldn't be a chewer any more, so I do not think there is a need for the biter apple spray. Just take one day at a time, and love him very much, he is going to be scared and confused, as he has been in his current home for the last 2 yrs
Can't wait to hear all about him and see some pics