From your partner's prospective. I can tell he cared. But it's not his job to fix you. As someone who has recently seperated from someone sucking away my emotional energy through his problems I can see his side.
I got with a guy who came across as together, solid and happy. But in a few short weeks I realised he was depressed and had carnage behind him. All around him was broken relationships. Money problems. Bad days. Stream women that had hurt him. It was a mess. But because he had tried to kill himself the year before I stayed. I let him talk. I told him how wonderful he was. I complimented him. I forgave him and let many things go, such as shouting. Swearing. Silent treatment. I lent him money when he couldn't get to pay day. Because I knew he barely ate as it was. I hated the thought of him struggling.
Over time I thought every other day I need to go. I need to leave. I need to stop. I need to get out. But I stayed for a few more weeks. Things got worse. He moaned. I listened. He had an off week. I excused it. I sent him gifts to cheer him up. He in return was talking to another woman or two.
I was on egg shells. Forgotten I had needs. Forgot I mattered. I didn't know how to focus on myself anymore. I was lost in him and his bluddy problems. The whole reason I got with him because he seemed funny and kind and happy. It was an act.
When we split he yelled at me. Blamed me for everything. Never thanked me for the stuff I did.
When I got away I was sad. In emotional pain. Lost. Confused. It took me quite a few weeks to get over him and several more to process things. I still loved him and cared. I like your chap had taken his problems on and tried in vain to fix it. Money. Presents. A shoulder to cry on. Ears to listen. I helped him set up a shopping account etc. Helped him order stuff for his house. I rang him at 3am if he was awake and in pain because I cared that much. I really did and i didn't care about sleep if he needed a chat.
Now I'm on the other side. I am relieved. Relieved because he was making me sick. He was making me anxious. He we lying to me. Taking advantage and being selfish. Instead of us enjoying a balanced realtionship. I was caring for him whilst he had allsorts in the background I was not told about including another woman or two.
I'm not horrible. I understand mental health and everyone needs a good person by their side. I would never want anyone to be alone on top of struggling with life. But in my case with him I didn't want it long term and why should I have? He was 15 years older than me. He had made his choices in life. He choose to drink, cheat, lie and leave his young children. He choose to fall out with his parents and siblings. I didn't want those things. I love my family. I like being around people. He had nobody around him anymore because like me he had pushed them all to give up.
What I actually want is someone to take it in turns with. Balance! Someone to invite me to his for dinner one night. Then I return the favour. Someone I can talk to and they know they can talk to me. Someone honest and prepared to put the effort in. Share laughs over a drink and talk.
Your balance was totally off in your relationship. It was not fun. He was looking after you far too soon. Your problems with money and your health meant he was doing what I was doing. Looking after you but who was looking after him?
You didn't deserve to be kept in the dark about the lady friend. I wasn't talking to anyone else so it's different in that respect. But the way you responded with violence and anger. You should have kept yourself together and let him go.
In the future I suggest you find the balance. Simple things. Such as taking it in turns to cook. Enjoying a walk or a drink together in the garden. You should be best mates almost with a partner. If you can't enjoy the company then the sex etc is irrelevant. Regardless. It's give and take. You didn't seem to give very much based on your posts.
I can imagine emotionally he was just exhausted and the other woman is perhaps lighter and more on her own two feet. Doesn't mean they will last. But I can see why he needed someone abit more positive to chat to. Sorry. But that's my pov.