potty training advice

okay so i have a almost 15 week old pit bull-mastiff mix that i have had for 4 weeks. he was a rescue after being left at a fire station with his litter mates (i did a dna test to confirm his bread). first things first, potty training, we are currently letting him out every hour when out of the crate and every 3 when he is crated. important note, i work at a vets office so he comes to work with me 5 days a week and is crated the entire time he is there (he has never had an accident in his crate) however when he is not created his still having frequent accidents if he’s not let out right at that hour mark. i live in a townhouse so im needing to walk him every time i take him out and honestly going out any more frequently just won’t work. he gets a high value treat and praise when he does go out side and is ignored when he goes in the house (no punishment, yelling or putting his nose in the mess). so i guess my question is should i be doing anything more when it comes to him going in the house? i use an enzyme cleaner to clean the waste with to hopefully get rid of the smell