What to do now... ? hmmmm, good question.
Really I think it's up to her. There will be no babies with your shared partner it sounds like. So you can both let her know that, there will be no living together it sounds like, so you can let her know that too. It sounds like it's not okay for him to just drop everything and go to her, so she shouldn't expect that either.
So where does that leave things...? well, you are willing to share your time with her to a point. What is that point? how much time? when?
You are willing that she be in his life at all... that is big!
You accept he loves her. that is big! and a lot!
You seem to have some very clear boundaries and so does he... she now has to figure out if it is worth it to stay with him knowing those boundaries. She can negotiate those and it will be up to the two of you if you are willing to budge on any or all of them. If you aren't then again she will have to decide if it is worth it to stay or go and find a man who is able and willing to join her on a journey into parenthood and cohabitation... possibly with your partner on the side.
This is how boundary setting works... making compromises until everyone feels comfortable or everything ends because it just isn't going to work.
You are on the right path I think, you just seem to need some confidence in that... just because she is nice and you enjoy hanging out with her doesn't mean you should compromise what feels comfortable to you. The image of her will change pretty quickly if you compromise as resentment will rear it's ugly head and you will end up hating her. Stay firm and pleasantly adaptable until she brushes up against your boundaries and then, with some assertion remind her where the line is. She will have respect for this and know where she stands with you, as will your partner.
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