This is what I think. Note I am age 64 and married for 24 yrs now. However had I not been diagnosed about 4 yrs back, and put on medications, I know my wife would have left me.
I know next to nothing about swinging. Never did it. But I do believe a marriage without trust is one big way to destroy it. There will be little time of relaxing.
The other thing about BP marriages, all the cards are stacked against such marriages. So called normal people marriages have a 50% divorce rate. With BP marriages, it a 90% divorce rate.
I think the only way you both will avoid divorce is to both work very hard at keeping it safe. I also believe without counseling there will be little chance it will work.