Of course it's not animal abuse! As LONG as they are still getting exercise and being able to get outside, etc. I think a lot of people have this perception that puppy pad trained dogs just live in the apartment 24/7 and never get outside. That, to me, is
not cool.
I don't personally use puppy pads, and don't think I ever would or could (Jackson refused as a puppy even) but being up so high in a NYC apartment would definitely prove difficult to potty train strictly outdoors. I just don't like pads and prefer for a dog to go outside. But like I said, in your situation, that WOULD be tough.
Have you thought about those potty patch things? They're, like, grass sort of. Except not. Google and you'll see some info.
I'm glad he gets to go out to dog parks and exercise still! Great socialization.