Husband had an affair with our neighbor, he doesn't know if he is in love or lust and should be with her?

my husband fell in a pit of ual exploration with our neighbors 4 years ago who were swingers. he and her began getting closer and more intimate with eachother, she got a divorce due to him emotionally supporting her and telling her should could do better. they continued seeing eachother independenly for the past 2 years. I didn't know or suspect anything. until my husband left a note for her that got back to me by her exhusband who had suspected they were seeing eachother but didn't have the proof until finding this note. I then was informed about the 4 yr past that went on. but was told by my husband it was over to later find out he was still lying, I moved out asked him to figure out what he was going to do, he asked me and the kids to move back home but he can't seem to stop thinking about if he should have went with her or us. he says he doesnt know if it is lust or love. when I moved out he never told her, she found out through her exhusband who I get ongong info from about the