First off luvsjack, I just want to tell you how sorry I am, it must be so terribly difficult seeing your child in a bad relatinship like this and wanting to help so badly but having limited things you can do.
I don't have much real experience on this stuff, other than helping the friend of my oldest when she was engaged to someone that was along these lines, which isn't quite the same thing---but here is my best advice anyway (so take it with salt):
The biggest thing I owuld do is STOP talking about the rumors of trying to get back with the ex, what he did to the ex, etc. Becuase they ARE rumors and you don't have concrete proof, and eevn if you did have proof abut how he treated his ex, your DD is likely to see that as not relevant to how he treats her. The more she perceives your concern coming from gossip about someone else (even if the gossip is ultimately true) the more she is going to refuse to see/believe your concerns about how she is treated and the more she is jsut going to defend him and feel he is unfairly under attack.
SO, I would stick to only talking to her about specific things you know are happening TO HER or between the two of them, along with talking about what
abusive relationships look like and how they start and how these things mirror that.
Bring up that you are concerned about how she always seems to be feeling guilty about simple things like visiting you and that isn't really healthy and ask hre why she thinks it keeps happening. Give her openings to think about it for herlsef, think about what is happening to her . . .
Same with the wrestling. Als how she feels about stepping back from it, what is she thinking of doing now instead. Get her thinking about HER opnions about it (that one is a bit interesting, at her age it wouldn't be all that surprising if she wanted to pull away anyway---it could happen that she was enjoying it but also doing it becuase you loved seeing her doing it, it meant she had time with her brother, etc and she didn't see any clear path out from that when it turned out not to be her thing (heck, she might like this guy partially becuase he gave her an excuse to back away some without feeling like she had ot make the decision herself). So, ask questions, express concerns ("I worry abuot jealusly being equatedwith love" "If you are not interested in persuing wrestling anymore, that's totally OK, I just hope it's becuase YOU want to try different things, not beucase you feel pressured to stop due to A's jealousy" etc).
I guess, to the greatest extent that you can, I'd try to be there for her (he complains about gas $$, you drive to her and have lunch with jsut her once a week, take her out, etc) and express your concerns about specific behaviours/emotions she is having with no ruor or outside sources, share with her about abuse and what it looks like, especially early on (print up some lists fromn reputable sites so she knows you are not oulling this out of thin air) and make sure she knows you will always be there for you if she needs you.
I wish you could just force her to see reality, but you can't so the best you can do is not make her forced to feel she just choose between you and him and hope that allows her eventually to choose herself.
(oh, and the panic attacks could be fake and jsut manipulative, or could be real. Sometimes people with uncontrolled anxiety and depression handled that feeling of lack of control by trying to control and manipulate others----that does NOT make it ok, but I think if your DD is living there and seeing what she deems to be real anxiety issues, it is important not to try to mninimize those ar insist they are fake--doing so will undermine your credibiity with her, but you CAN talk about that he is responsible for his bahaviour and getting help for the anxietz if he needs it and should not use it as a crutch or an excuse, etc
The insecurity runs deep with this one.
