Awwww gawd Asset !
This is awful !
And from part of your post it seemed you guys (all 3) were doing great for awhile !
So, I wonder what changed - REALLY ?
We only have what you offered and there's probably some stuff we don't know that would be enlightening. But from what you've said, consider this as one possibility...
It seems that maybe when trouble started was when you opened up about your feelings of being left out. That seems it may have set up a competitive environment for starters. But you were absolutely right to do it !
Now...add to this a 'possibility' that this evoked some guilt with him. If he's really a decent person it would almost have to. Remember - you're all new at dealing with a complex thing here.
And some people don't have good skills for dealing with guilt. So his reactions toward you MAY be driven partially by that. Be that as it may - it's not the way it should be going down. You guys ABSOLUTELY have got to get talking but, in a non-confrontational, non-aggressive way ! That's another skill to learn
So as hard as it is (and it IS hard), I'd try to get some emotional disconnection from the current state everyone is in. Try to take a deep breath and take the pressure off everyone.
These things go in phases and you can work through them. That doesn't mean you'll be a happy little triad in the end. It doesn't mean you won't ! But what you are going through is not at all uncommon and many others have been there too and come out the other side wonderfully. A lot will depend on the true connections between the 3 of you and how good you get at the NVC thing (non-violent communication).
I'm sure some others will weigh in here to help you. There's some very insightful folk hanging around here who have lived this experience too.
By all means keep us posted. We hope for something good to come out of all this effort you will (and have been) putting in. Because it's all worth it in the end if you can get there