Short background: married for 7 years - i love my guy-, I have BS10, and SD12. BS is easy, SD is a complicated and manipulative, DH is weak and guilty. the dog is OK

DH and I fight only about 1 thing: SD12. that is all we EVER had problems with. i took care of the girl for years, he was fine wit hthat until i asked for help because she was VERY hard to deal with. he called that "complaining" and that "she is a girl, bla bla bla,,you know the story. So i disengaged and now after I disengaged from her 7 months ago...DH got the guilt all over again....kind of "a mom abandoned her when she was 2 and now you abandon her too, poor thing". at one level i agree that she did not have a great mom and after i tried for so long i did kind of give up too...true. at anohter level i think that she is lucky ot be in a stable family that porvides for her and takes care of her and that he needs to address those emotional problems with love, time, counseling ,etc. not me.

the girl has clear emotional problems, she is very closed, lies a lot and does not want to be part of this family. she manipulated daddy very well and all the typical things that you all understand so well.
the problem that we have at hand now is that im numb, i no longer engage with DH in conversations just in case SD comes up and we end up fighting, I don’t have the strength any more. I cant “expose” my emotions, open my heart again and again, I cant have hopes and every 2 months be deeply hurt again.
we talk about the day, the weather, the news, extended family, work, etc...there is no trust anymore, I cant be me, I don’t even enjoy sex…there is something very broken. im so hurt for all the things that were said in fights like "i pick her every day of the week over you" and lovely stuff like that, Im so tired of always being blamed and guilty of all these things. Im a very open, funny, social, warm person who loves kids and kids love me and at home im America’s most wanted 
im not sure i can put my heart in this anymore. Before i would be "lets talk, lets figure this out, let me tell you how i feel, i dragged him to counseling, wrote letters to him, gave him books on the subject, I even told him to take a look at this site, etc, etc". now i kind of put my energy on my life, my job, my bio son, my sports and hobbies. he does the same...i take care of my kid, he takes care of his...this is not a family. im not happy with this and i know that it will simply disintegrate if we go in this direction. I cant be the engine of this anymore, it is exhausting and depersonalizing. Is he too much of a coward to show his feelings with me? Why? Does he want this family after all? Is he still here because it is too much of a hassle to leave? How do you know if somebody loves you in a situation like this? i no longer have the heart to keep pushing and pushing by myself, it is not healthy...so, is it the end? any advice?