That is a complicated situation you have there. You had a long time "hobby" of flirting with women-- are you still doing that?
Is there any chance of you meeting your wife's bf? Are you interested at all in MFM sex? Is he? Even if the answer is "no," to that, meeting him and having a beverage and a chat might help your jealousy.
Now, as to you and your wife moving to the country and her being a stay at home mom, but the kids gone to school all day and she's bored and lonely... why did you 2 do that? She needed a friend. She could've met platonic friends eventually, joined some social groups, but instead she's got a lover.
Do you want a lover? Surely flirting with other women online was sort of like having lovers, getting the hormones flowing, probably you getting aroused from time to time, masturbating, or bringing that excitement to the bedroom with your wife. Do you want to take it to the next level? It's easier to find someone to date one on one than it is to arrange 3somes, especially if you want real connections and not just casual sex.
Why has your sex life suffered since she got a lover? Is she worn out sexually with nothing left for you? Or does your resentment/jealousy seem so upsetting/boring/scary to her, she is not excited by you? Or are you so jealous you've lost your sex drive?
OK, lots of questions. Where to go from here? Better time management? She only sees him once a week (at least for a while until you two sort out the issues)? Less time spent texting? More romance between the 2 of you? Not just TV watching, but going out on day trips on the weekend, dinners out, a show, an event, a long walk in nature, massages, flowers, candles, wine... All the things new lovers do. NRE can often make poly noobs neglectful of their primaries. Just saying she "still" loves you isn't enough. She has to show it, keep your connection healthy, exciting fun. Does she feel no gratitude you're on board with her having another lover in her life?
Love withers under constraint; its very essence is liberty. It is compatible neither with envy, jealousy or fear. It is there most pure, perfect and unlimited when its votaries live in confidence, equality and unreserve. -- Shelley
Mags (poly, F, 61) loving miss pixi (poly, F, 39) since January 2009, living together since 2013
"Master," (mono, 34), miss pixi's Dom for 3 years