Potty training rescue dog

Hello there, I recently (as in 2 weeks ago recently) adopted a 5 year old pitbull. He's a great dog and super easy to train, except when it comes to potty training and kenneling. First and foremost, he will only poop inside, never outside despite me taking him on 4 long walks a day. It doesn't matter how long I walk him for, he will pee but refuses to poop and then the second we get back to the apartment he will poop all over the carpet (my roommate is at her wits end about this.) And despite growing up with dogs and being a dog groomer, I have never potty trained a dog so I am at a loss as to what I should do in this situation. Kenneling is not an option whatsoever. (I attempted to kennel him the first few days I had him while I was at work and he flipped the kennel over the first day, had diarrhea all over himself and the kennel the second day, and then the third and final day I tried kenneling him he flipped the kennel once again, pooped all over, and somehow, dislodged one of the sides of the kennels (scratching up his nose badly in the process) and escaped from the kennel which is a mystery to me how it happened, so I decided kenneling just wasn't a good fit for him). He does infinitely better when he is not kenneled and has no problems save for the not pooping outside and only pooping in the house. If anyone has any possible advice I am open and willing to listen/try anything (and I know it will be a slow process but I need insight on where to at least start).