1. Covering the bills for 3-4 months while you are 38-40 and your girlfriend is 18-20 and starting a business is not really “above and beyond” and certainly doesn’t entitle him to not work again and live off the next 40 years of your prime earning age.
2. You asked if you could go on a girls trip? If what he spends his money on is fair game, same goes for you.
3. The silent treatment is manipulative. Your communication is not the poor one here. Sounds like an attempt at gaslighting too. Budgeting for a future trip is responsible, not an “excuse”.
4. The manic/depressive stuff might be something to see a professional about (and I am not one), but I also wouldn’t be surprised if it got a fuckton easier to manage without him in your life.
5. He doesn’t want you to share with anyone because he knows he’s a leach on your energy and probably manipulative/emotionally abusive. Isolating you should really have been step 1, seems he’s late to the game on that. I would not be surprised if he starts complaining about the therapist too.

Honestly if you’ve built a business you can live off of at your age with this boy dragging you down, you sound like a kickass person and would have an even more awesome life if you dropped him.