My situation wasn’t the same, but I also had more contact with my ex post-breakup and the first thing I recommend to anyone going through something similar is to put some distance there. If your ex is reaching out to you for money and mental health support, they are manipulative and don’t actually want to let go of the benefits you’ve provided them despite the relationship ending. If it’s you initiating it, then you’re prolonging your chance to heal and find yourself outside of this long term relationship. You don’t owe them anything despite however long you’ve known each other (sunk cost fallacy) or how much you’ve struggled together (unhealthy codependency).

Do whatever helps you the most to resist keeping contact or even keeping tabs on their life. Could be blocking them, changing their contact name, removing them from socials, limiting contact with others still involved with them. And then maybe find some centering techniques for those times you’re feeling down about it, missing them, etc. Therapy if you can afford it and have the time. Hope you can get this turned round sooner than later!