Ok, first a hello, then a lot of pondering.
The thing is, as long as you are seen with a man, known to date a man and publically acknowledge you are dating a man you are assumed to be straight. No way around it. As long as you are seen with a woman, known to date a woman and publically acknowledge you are dating a woman you are assumed to be gay. Welcome to the club.
I understand the craving for a social recognition for your identity. You can hold on to that hope and for example decide that while things with T are wonderful and peachy, you are continuing to look for a female primary to have a pouffy wedding and kids with.
As to coming out, how about doing it in non-verbal ways? Join a Facebook group, wear a badge, post links to LGBT equality campaign websites and videos etc.
As to dating; not many true Lesbians are that keen on non-monogamy, and especially not happy about the prospect of sharing with a dude. There is a sizable number of Lesbians who won't even date bi women because they fear (some rightly so) that they will eventually be tossed aside for a man.
In your situation, the best bet would be online dating, where you can be upfront about what you are looking for, and also not keep anyone in the dark about your boyfriend. Most likely demographic to target would be other poly bi women. If I were you I would make it very clear that you are dating separately from your boyfriend and no unicorn-hunting is implied or assumed. Are there women's groups in your local poly community or bi groups in your local LGBT community? While the emphasis tends not to be on dating in those circles, at least you could meet other women in similar situations.
And onwards on the speed-advice line: maybe the fact that you feel little jealousy or dismay is because you deep down knew all along that this could happen with T and R? From what I've observed, notalgia shags with exes are pretty common, and usually good for one partner to realize why the relationships ended, i.e. that it's only nostalgia and nothing else. However, I've seen that usually the other ex-partner is secretly wishing that the relationship would continue, and keeping them hanging on is just mean in such situations. Good that T broke things off with R!
Me: bi female in my twenties