I reckon the new baby on its way is probably a big contributor. Little people pick up on changes, even if they can't verbalise it. ALso (i don't know if you want to hear this) even if you get things sorted out now, they may start up again when baby arrives.

I don't know if this is the right way, but with my DD (before DS arrived) we just tried to re-direct attention, and tried to do fun active things with DD to enjoy the last few weeks as a family of 3.

Is there somewhere else he can nap that he can't trash? Maybe letting him sleep/rest in a spare room or in your bed.

it is tough