loving best friends girlfriend.. dont know how to stop feeling hurt

About a year ago my friend t.j. introduced me into his girlfriend. since then the three of us have hung out alot. About a 2 months ago they got a room together. My friend t.j. had gotten a job and was working night shift. Me and his girlfriend would hangout all the time and still do because she doesnt have very many friends and t.j. can trust me with her. Since they have moved into a room with each other things have changed for them though. Just like all her peers and family told her things would get harder and worse, and it has, they argue almost twice a day and she crys like over 4 times a week. I cant even tell him to quit treating his girlfriend the way he does because he is very jealous about certain things and inevitably i could see me and him not talking because of a small issue such as me intervening in their relationship. It makes me very angry to see him treat her like that and on top of that he smokes weed all day and spends at least 10 $ a day on it and he lost his job 1 weeks ago and is barely looking for another..anyways while he was working at his old job me and her would have good times and got close a couple times (not kissing but close) i know she has feelings for me but she cant pursue them.. i have feeling for her but i obviously cant pursure them and i cant show them around him either because he as i said is very jealous even if i commented on her beauty. What hurts me the most is knowing how much better i would treat her is she were mine. and that she knows that she even admits i would treat a woman much better than he has or ever would. see the problem is i knew him before her.. in fact for years iv known him but we've had our problems too.. but it kills me knowing what happens in their room at night even the same days he makes her cry.. they make up because he says something fake to make her laugh and smile then everything back to normal.. next day he does or says something and shes upset or crying again..one time me and her got pretty close in details i was scratching her back and massaging her back when she layed over me and basically got in my face (she was half naked) and she told me not to fall for her because she would hurt me.. then she got up and kind of did like a stressful exhale.. i know she wanted more she wanted to connect because she was telling me how much her boyfriend neglects her and that is why she does what she does.. i guess in a nutshell we both really like each other, he treats her like crap ,but she is so attached to him she cant leave.. its complacence.. and i am just hurt because were close but t.j made some stupid joke/ remark about scratches on one of their roomates(a guy) and he said " o you like to scratch i wonder how he got that" and obviously it wasnt from her (it was actually from a pet rabbit another roomated had) and he acted like he was suspicious and now she says she cant even be close or say certain things to me ever not even alone... it doesnt bother her as much as it bothers me.. she has love but im still looking for love..

im not sure how to feel, or how i feel, what to do, what is my position in this relationship..

so far im just like the good friend who does favors for them and hangs out with them alot..
sometimes t.j. will get jealous about how me and her are togetheralot or every once in a while finding a comment on a text message to her and he'll be like "see this is a 3 way relationship!.."

i know this was long but i had to post it and get it off my head and hopefully get some insight..

??