Well, his dream seems like his #1 priority, so he probably can't think well of the relationship when he's starting to realize his dream is fading out.
I read about negative symptoms happening to men who turn into stay-at-home partners - they can develop that kind of complaining and can even develop depression.
I think going deep into his heart and understanding that he is devastated by his dream's outcome and being empathetic can ease his pain. It can take time, but it has to start with LEAP (Listening, Empathy, Acceptance and Partnering). You're partnering greatly as I see. Eventually you're gonna have to be there for each other, through the highs and through the lows.
He's not a loser, but feels life a loser. I'd say he's quite the warrior fighting for his dreams, you should be proud of it!
He may be depressed. I think he should get as much help and support as possible. Start with yourself, offer your heart and time for him, use both your free time to be there for him, even if it means staying at home and just talking things out at times for instance.
If you've really reached a point your help does nothing, consider a therapist to help guide him to a more suitable path regarding his dreams on one hand, and the current situation on the other hand.