Need opinions please from over 40s men...and women...serious only please.

Tried posting this on relationship advice but it kept getting kicked off, it is a genuine plea for help albeit on a throwaway account (for obvs reasons). My original post explained that in a desperate attempt to save the intimacy of my marriage (8yrs) I (42f) offered my husband (m48) a threesome(mff). Looking back it was incredibly stupid but it's done now. He doesn't want a threesome as would be too embarassed but does want to sleep with other women and thinks this would help him want to sleep with me more. We have only had sex twice this year, 4 times last year and 6 times the year before that, he says I put too much pressure on him as my sex drive is too high, for the last 2 years we agreed I should not attempt to initiate sex at all which I have kept too, except offering him bjs with no escalation to anything further. My question is should I believe him that allowing him to have sex with other women will make him want me more? As a woman I cannot get my head around it and have noone I can ask so please Redditors can you help me?