You are welcome
That new bit of information is a bit clearer, at least from my point of view. It's obivous that you will never form a triad (three persons, all involved intimately with the other and in love) but a vee relationship seems possible, especially as everyone at least cares for the other(s). This is beneficial for such a constellation.
What seems to need some time is everyone adjusting to this thought and situation. J isn't completely sure how to handle this, what he wants for you/ the three of you and what he wants for himself. Give him some time to figure it out. He is right that rash decisions aren't called for when you try to handle love. So give everyone some time to sit on the problem and find an agreeable solution for himself for now.
It's understandable that each of them wishes for a 'stable' position in your life. You described them as mono and they wish for a two person relationship ideally and want to share their life with you. Those close relationships are possible, even if you have more than one. You have a great starting point, because everyone involved cares for the other and strives for their happiness. That's great.
I would suggest that you just wait for all the new information and possiblities to sink in a bit, get together and talk about everyone's feelings and wishes for now on a regular basis and try to find a solution that everyone can live with in the long run. Communications is the most important tool in any relationship. Use it to your advantage and try to make the best of this situation.
Facts: 30, female, bi, v-type relationship with Sward (husband, straight, mono) and Lin (boyfriend, straight, mono), poly-fi and co-primary.