Hy

I've been together with my love partner for 2 yrs now. We've been both living in different countries so this relationship even though it was tough,it was still going very well. Before he ended up in a hospital in December last yr and was diagnosed with bipolar disorder & DP we were madly in love & closer than ever. After all that happened, as you might imagine...he has changed.
For 1st 5 months this yr he would barely talk to me. Couple of times he even tried to break up with me. Over those 5 months,all that stress broke me,mentally,emotionally and physically(including healthwise) completely....to a point that I almost ended up in hospital several times.

Then one day,after a huge fight,he was back to himself and more or less(after some switches that lasted for only throughout the night) he stayed that way...it seemed like everything was doing ok. We were slowly starting to plan on seeing each other next yr...there was no pressure involved,I know I can't do that to him,and he reaction to was great.

But few weeks ago, he's been going through training periods, he said that they were becoming more and more intense(somekind of stress training),and then on Saturday,he switched back to that awful person. I didn't even know because he wasn't online over weekend,only on Monday I found out about it...he had hypomania.I started to fear that this is just a beginning and now...after this weekend...he hasn't switched back :'(
What's even worse,since day one(which is 4 days now),he's been asking that we break up. On top of that, after he saw that I wasn't budging, he's been blackmailing me that if I don't accept him as just a friend,he'll remove me from his life completely. I honestly don't know what to do :'(
I've tried to stand my ground, I've tried to reason with him,I tried to fight him...nothing worked! The only thing that I haven't tried is cry and blackmail myself,but I doubt it'll work because that side actually enjoys to see someone suffer,I think it feeds that behavior, and also I couldn't do something like that to anyone

At this moment I'm panicking and worried that if I call his bluff & he goes through with his intent,I'll definitely never see or hear from him again! :'(
I don't know how to stop his erratic behavior and stop his intent
I don't want to loose him! We've been together and went through so much already..and I know that when he switches back and sees all the damage that horrible side did...he'll never forgive himself :'( ...I need to stop this ASAP...but I don't know how,I don't know what to say/do
Please,I'm in desperate need of your help :'(