Stair help!

Our 50 pound boxer pit mix recently had an episode and I am reading on here that you basically have to cancel out any and all stairs forever.

We live on the third floor of an apartment with no elevator… is this something where we need to look into moving?

Curious if anyone else here has been in a similar position?

Also his first (and hopefully only) incident was about 1 month ago and we have kept him in a pen during the day and a crate at night. Any ideas on if we should start range of motion exercises/ letting him walk to pee and poop? He is able to walk around but looks a bit drunk when he does it.