Scared and Hurt

Hi all. I'm new here but I need some help.
About 6 months ago I fell in love with the most wonderful person I think I will ever meet and he he had baggage but it didn't scare me.
A couple years ago, he developed AN in a suicide ward. He struggled for a while but eventually got weight restored and could function just fine but he never actually dealt with the mental side of things as he 'recovered' by trying to stay in a good mood during the day and binged at night.
About a month ago, he started to eat less but I thought it was nothing (I didn't even know he struggled with an ed at the time). Two weeks later, he had cut cals so much so quickly that when he had an anxiety attack at the same time as a low blood sugar episode, he over-treated it and was unable to move, had postural low blood pressure. He was diagnosed with refeeding syndrome and not allowed to leave until he was better. It was horrible to see. After the ng tube was removed, he was placed on a certain amount of calories which was extremely difficult for him for obvious reasons but he wasn't even underweight. Less than a week later, they finally released him from the mental health act so that he could go home since they didn't have any beds in the MH ward.
Coming out of hospital, to begin with, he was fairly okay. He was able to eat all his 'safe' foods and was on what would be an extreme diet for most but a huge improvement for him. This fairly quickly changed however as he restricted to a certain amount of his BMR as safe foods became unsafe over the following weeks. He had told me multiple times that he didn't want to improve because he couldn't so there was no point in trying. It was easier to give in.
I, of course, was terrified and developed near-constant anxiety as I was triggered by so many things. I began to develop AN and thought that googling stuff would help when I was anxious (spoiler alert, it made my anxiety far worse). This continued for a couple weeks (that felt like a year) until he finally opened up to me about how much it sucks to have an ed. He's tired all the time, easily agitated, hates his body and can't think straight. I was so glad to hear him talk to me, finally, about things. This whole time, he wouldn't be able to talk to me about any of it. He would just shut down and I would just have to shut my mouth or it would upset him more. Following him opening up to me, I realised how important it was for me to recover so I began to. My (initially forced) increased mood and aversion to talking about anything to do with it improved his mood to the point where he expressed how much he actually does want to recover but it's so difficult. He also deleted his calorie counting app, removed locks on his phone and said he'd increase. He says that he gets this extreme nausea and anxiety when he tries to eat anything he's not 100% with and how impossible it is to force himself through that.
Unfortunately/fortunately, his metabolism is not new to this kind of restricting. He's not overly weak, his heart isnt beating too fast or too slow, he's sleeping okay and hasn't had any of the more concerning symptoms such as fainting. He's definitely much skinnier but he said it's really frustrating because he can't lose weight as fast as he wants to while not being tachycardic or constantly exhausted and depressed/angry.
Will all that said, I genuinely believe he has the potential to decide that life is worth living properly (since he's starting uni soon and is looking forward to our life together) and begin recovery in some way. Due to this and his intense fear and anxiety with hospitals in general let alone an ed ward, I think putting him in patient should be a last resort.
With context, here's some questions.
1: When is enough enough? I know his body is eating it's self but I still think he can and had time to improve but I don't want him to die or have irreparable damage done (people struggle for years with this, right?) But I don't know when to make that final decision to have him admitted. Are there any big red flags I should watch for in his behaviour that would mean he's gone/about to go too far?
2: He says that when he's using other unhealthy coping mechanisms, he has very little anxiety and a genuine appetite. I know it's not sustainable but I thought it to be a lesser evil considering it's not like he'd eat if he wasn't using. Is this normal or even helpful?
3: He explained to me how much guilt and shame he feels about effecting me so much. He's expressed when he's distressed that he wants to live alone because then I wouldn't be triggered by him and he would feel less guilty about putting more on me. The thought terrified me to begin with (and still does) but could that actually help anything? I fear he'll sink into a rut of depression and loneliness as he gives in and lets his ed progress back to what it was when it nearly killed him the first time but they do say distance makes the heart grow stronger.
4: what are some things I can do to help me? I'm already meditating more (which is helping with how reactive and emotional I get when triggered), I'm seeing a therapist more, I'm talking to friends more, reminding myself that he is genuinely generally happy, writing my feelings and thoughts down. I am doing all the right things but it's so exhausting. I just have this constant and ongoing fear and anxiety in my chest that I'm watching him die and not doing anything about it even though I'm doing everything I can.

I have never thought I could be so perfect for someone let alone that someone could be so perfect for me and I'm terrified of losing him.