Good luck! After years of being free to be with whomever you want, this will feel like going from being poly to being mono.
Some monos, however, are more accepting of various activities coming short of "going all the way." It's disturbing your new female lover was jealous of your h even "being affectionate with" a friend. Even if actual sex with others has been sporadic for you anyway, think about this. How much can you do with others? Look at hotties on the street and make admiring comments to each other? Cuddle, flirt, dance sexy, give massages, have non-sexual but intimate dates, do non-sexual kink play, chat online, talk about sex without having cybersex, have cybersex, cam shows? Is looking at porn allowed, for some kind of non-fidelitious release?
My gf and I are not poly-fi, but I like my ability to do all on the above list, because my ex was so jealous even when some looking or mild flirting occurred, it felt very confining and controlling. I think even if I was in a poly-fi arrangement with another person or two, I would not be able to give up those other entertaining and nourishing activities.