>I have heard that guys appreciate it when a girl says they understand how busy they are (especially when it's true I suppose?)
I'd say UNIQUELY when it's true, and even then, not all the time. It might just sound a different way to say "yeah, your other stuff is more important than me". Really, best leaving them alone when they're busy.
The ball is on his side, just wait for him to throw it back. If anything, to off some pressure off your shoulders, you might in a few days (and I mean that like a week or so) send him a quick text to cheer him up with his stuff, and don't make it sound like an answer is expected, and don't be verbose about it.
And on a more positive note for you, if he is indeed interested, he might be waiting for time where he's more relaxed to do stuff with you. Hell he might even be stressing about this too. But don't focus on this. Keep yourself busy on the side too, and stuff will go down its way.