how do i restore my Life?

Well this is very complicated. me(m56) and wife (f54) have been married over 30 years. We have many kids and sex has been a big part of our relationship. She had sex with at least two other guys before me and i had some experiences but not as relationships like she did. She was/is a strong sexual partner really works the body into it but fights me back too but im persistant all these years too. So maybe its a bit bipolar in retrospect but im confused. We sporadically did some swinging that really amounted to a few mfmf encounters and mostly mfm type play. She went along and got into it and really seemed ok with the multiple men giving her a good time. She had one favorite guy that she actually went to see two differnt times on her own. Now that is a brief back story about us. So over 8 years ago my wife’s niece (then f18) was working for my business. My wife was not making any time for sex with me happen for many days and Christmas was a day away. I stayed up for a day and a half shopping and doing other holiday preparations and at work i alwaysa cooked a big lunch for the workers. This niece was helping me and she talked dirty and i had heard that her older brothers had played sexually with her ( talk nothing confirmed). Anyway i made a pass at her offered sexand she refussed. Its good she refussed i was exhausted and made a bad judgement i think being that tired clouded my thoughts. It blew up and i apologized to all people especially my wife. She said she forgave me we worked through it and i put it in my past never repeating anything like that with family. Now we played with other swingers a bit since mostly males. Time has past and her libido is way down. I try spark up what we had but now the sex is rationed off to me and everytime i try to initiate sex sometimes a day after we just had sex i get scolded about her not needing it so often or she ate too much or other excusses i told her I’m percieving a lack of interest from her and turned into a hour long reason excuse and finally condeming from her that made a pass at her niece and that is why she has stopped trying to swing because she thought it was keeping me from doing things like trying to get with her niece. Its not easy to type the details exactly as they are but in general we used to play and it was enjoyable to both of us but now shes gone cold and after years sounds like the grudge is still there about the niece. My job changed and im now making a lot less money and im tied in with her family so divorce means losing far too much. Also for the last six years the thought of us playing has been my sanity to get through work for less pay. Im depressed and sex is my relief. Im upset that my world is crushed. Help me try to restore her libido ir could not have been all an act for all those years and she asked me for permission to go visit her favorite guy back then but she says she did all that for me to run with keep up with me. I personally think her libido is way down and since is not interesting to her she doesnt even try anymore. Again help what do i do Could it have acting for all those years and meet ups with people? Or is it acting now Or is she just going through the motions now just doing the minimum to keep me around