I was newly married when I had my accident. I was 90% body area burns.
You are probably right in assuming that he isn't doing as good as he says. If he was he would be trying to do better at therapy. I worked hard at therapy because I knew I didn't want to stay in the condition I was in. It pays off down the line. It also gets easier over time.
Try not taking things personal. He will be dealing with a lot of emotions and probably doesn't believe it if you say you can understand. He may even distance himself from you to protect you or to protect himself. Just keep trying to give him support. Are there any doctors, where he was treated, that could get him some help emotionally? It's hard to figure out how he should feel or what the future has in store. He probably imagines the worst or wants to forget about everything as though it wasn't a big deal. Either way, grieving needs to take place. It is hard to say how long that might take.