For me that's not sex. Sex is sexual intercourse for me. Sex, for someone else maybe indulging in a sexual act.
If I had had a date(if I was single) with a man and he fingered me or I gave him a hand job, I wouldnt tell my friends that I had sex with him. He wouldnt be classed as a bloke I once had sex with. Cause, for me, I didnt.
If me and dp only did the same sexual act over and over again, and that's all we ever did, then that would be a deal breaker for me.
If dp only allowed one sexual act, and that act being him fingering me whilst kissing me and talking dirty and wearing a latex glove. And that's all we ever did. Then no, I wouldnt be ok with that.
It does feel like the OP is doing the bare minimum, in the hope it keeps him quiet.
I think she knew deep down, it would get to this point. But ignored it until it was obvious he wasnt happy.
She could have tried to sort this issue between them ages ago, knowing that eventually it would be just boring. I expect he thought, at some point there would be some variety.