Even though your in this situation and its painful and confusing. YOU sound like you are thinking about it very rationally as you are acknowledging its triggering you and feels unhealthy. I dont think you need to feel guilty about that because its a healthy response in my opinion.
I also understand you are worried, and feel like you are the one who he is reaching out to right now. There is nothing wrong with being upset or worried about someone who is in this situation. It makes you compassionate. But knowing that you have to preserve your own sanity, health, emotions, and plans for your life - is really crucial. I lost myself for a while when I went through this with my husband.
When my husband was binging it was very hard, sometimes impossible to really talk to him because his thinking was so warped. I think in the case of a suicide threat its best to call 911.
Basically from what you posted, it looks like his pattern is to binge for days. He apparently did seek help at one point, has a therapist, and Im assuming a Dr. So, he has their support if he reaches out for it.
This is just another thing I will throw out there.. I have had mixed success with this one.. if you know his family, or any of his close friends, and think they might be a support or encouragement to him then contact them. It will be their choice in deciding what kind of involvement they have at that point. They can always choose not to get involved if they so desire.
I contacted my husbands family and it was pretty much a mess because they do not interact well with him, and basically always make things worse. However much later I reached out to my family, and they became the greatest support for both of us.
Dont feel guilty for stepping back during this binge, or for deciding you need to leave the relationship if that ends up being your decision.