That IS kind of lazy. I would be mad that he just broke your plans because he wanted to sleep in, and not tell you. He should have just been like hey, im really tired, do you mind if we get together tomorrow?
If you guys just got out of classes, its understandable being burnt out from school but that doesnt explain why he's not working at all, and he sleeps into the afternoon. I dont think that's good and Im not much older than you guys are.
You're not wrong in thinking he should be doing something with his time. Being understanding of a bad family situation is important though, if he needs to spend more time with his dad right now, then that's what he needs to do.
You never know what's going on in people's houses sometimes, even if you ARE dating them, his parents might be about to split or something. Just know that you'll see him when you can, and not to make a hard time for him worse right now. You guys really care about each other, so youll see each other soon enough.