Just a thought, I know you said your husband is very vanilla, but is it *possible* that part of what he finds upsetting is that you're exploring this new side of your sexuality with someone else and not him? Like, even if it doesn't come naturally to him, is there any chance that HE wants to figure out how to help you fulfill this urge and be the one leaving bruises on you but feels like you couldn't see him that way, or like this very experienced new guy would just outclass him to the point that you wouldn't be interested? Cuz if I were him and I did feel that way it would definitely be upsetting. Maybe he just doesn't know how to say it?
Me, 30ish bi female, been doing solo poly for roughly 5 years. Gia, Clay, and Pike, my partners. Davis, ex/friend/"it's complicated." Eric, Gia's husband. Bee, Gia and Eric's toddler.