I think there may be some confusion here...
No mention of caffeine in that study from what I can see.
Choline is a precursor to trimethylamine, which has a fishy odor. Normally, our bodies convert it to trimethylamine N-oxide, which doesn't smell.
In those with trimethylaminuria, an impaired version of the enzyme flavin-containing monooxygenase 3 (FMO3) is unable, or at least not efficiently able to convert trimethylamine to trimethylamine N-oxide.
I would seriously try some activated charcoal. Lmk how it works for you. I'm curious to find out.
Edit: I'm no expert, so you may not actually have trimethylaminuria...but you have the symptoms, which indicate trimethylamine making it through your body, unconverted. Its for that reason I recommended trying a trimethylaminuria treatment. And, as mentioned, activated charcoal is cheap and easy to find.