Honestly, it sounds like Marlin needs a dose of "My way or the highway". Because his bad behaviors sound so ingrained, it will take a lot of ignoring to do the trick and he'll likely go through an "extinction burst" where he will bark to the dickens to get your attention because it has worked in the past. However, you have to ignore him and let him go through his extinction burst. Once you "win" the battle at least once, the idea will sink in very rapidly.

He sounds perfectly capable of going outside without you getting up and he is certainly capable of going up and down the dog stairs, so let him do it by himself.

Have you considered doing NILIF with Marlin, as well?