I don’t know if this will help but try a lower fiber food. I am using Earthborn Primitive natural which is 2.5% fiber. Can’t hurt to try.
You said “I live in an apartment where I can’t let him out whenever he would like”….l’m sorry but living in an apartment is no excuse. You either chose to have a dog while living in one or chose to live in one after getting a dog; either way, apartment dogs are no different than home dogs. They get taken out when they need to go, unless you have trained him to pottty on pads inside.
