General Discussion

The only reason I can see him willingly resigning is if he becomes so disabled he can't appear on TV, or if someone convinces him he can't self pardon. The latter is extremely unlikely at best since there's no way to prove a president can't self pardon until it gets tested.

So he'll stick it out to the bitter end unless he's literally drooling uncontrollably or similar.

Then because he's been grifting and stealing, he will pardon himself preemptively for anything and fight any efforts to bring him to justice until he shuffles off this mortal coil.