There was an article years ago about testing the peanuts that were put in bowls on a bar.
They found they were contaminated with all sorts of things including faecal and urine. The also said construction workers were more likely to have cleaner hands than office workers. The dirtier the job the more likely they were to get thoroughly clean when they got home. Women generally wash their hands more than men.
Perhaps casually show him an article like this but not when he’d just been to the loo.
I feel you pain. I’d been asking my husband for a while to put the loo seat down before flushing. I didn’t used to worry until I read that the flush sprays contaminants all over the bathroom. I thought Covid was a good enough reason to remind him. Made no difference.
Like you there was a lot of difficult behaviour and he is now an ex.
He is showing he has no respect for you and as you say his other behaviours say the same. Any thing you say will be called nagging.
Or just buy a can of Dettol disinfectant spray, and spray light fittings, taps, door knobs regularly. I used to do this when anyone, especially kids had a stinky cold.
You could follow him out of the toilet and spray everything he touches if you want confrontation, but I personally wouldn’t.