The suggestions you have had here are great I think. I agree that you would do better to focus on yourself at this time. It sound like they have some stuff to work on in many areas.
This is sounding like it is turning into a friendship. She doesn't want you to spend alone time with him, you don't seem interested in being romantic with her, neither are available to spend time with right now and he seems to be unavailable entirely. It sounds like this went way too fast and imploded.
I think if I were in your circumstance I would negotiate alone time with both of them and together time. Regular date times that are discussed and followed through with until something changes. If you are only interested in him... then this is a vee and it might suit to start treating it as such (or did I miss something there). Spending date time with him and social time with both of them is what I would suggest. Why beat around the bush trying to make this something that is it isn't. If it ends up being a friendship, so be it. If the bonds deepen, so be it. One thing is for sure as far as I am concerned, time to slow right down.
It sounds like she is likely to be confrontational about alone time with him for you. So I think I would prepare to put my foot down about this. It is completely unreasonable to not have that as an option. Either you can agree to it and suck up how you feel, or not and she will have to suck up how she feels, or you can end the relationship. Private time is one of the most important things... actually, there is really no point I can see, for the long haul, that would make a dynamic such as yours work any other way.
What I am suggesting is to take the emotion out of this and make it scheduled in time slots. The emotion can come during those time slots. That way, you can sort out your life and look forward to scheduled dates and so can they; no expectations, no assumptions; some time to sort stuff out personally and time to let nature unravel what will be.
I think one text a day is reasonable... that can be negotiated too. If they don't text and you want to say hi, text them! There is nothing more damaging that expecting texts and not getting them... you create your own drama with that one I think.
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