DH farting problem ruining relationship

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So basically what it says on the tin. Married 4 years, everythings fine, really cant conplain at all except for the farting issue. And yes he's had all sorts of tests, diet changes, nothing helps 😣 he's massively self conscious of it, smell is putrid to the point of making me feel sick, and so embarrassing when visiting parents or with friends, I cant seem to get the stench out of the house.
Just to be clear he doesnt eat junk food as im not a fan, we eat healthy, weirdly it seems the more nervous he gets about his flatulence the worse it gets. The weekend was the last straw, I had to sleep downstairs as the smell in our room was disgusting.
He's had a colonoscopy, showed nothing, stool samples etc, theyre saying ibs as he's other wise healthy apart from the putrid farting which is ruining everything.

For me (ex vegan whose guts got increasingly worse until I reverted to an omnivore diet) I cannot tolerate ANY carbs apart from rice.

Potatoes result in the worst smells

Pulses result in the loudest noises

Wheat and sugar result in the most bloated distended and horribly uncomfortable (so cakes are the worst)

Brassicas and onions. All a bit rubbish.

Omelettes and stir fries, plain meat/fish and veg (peas), paella, tuna mayo salads etc are all gut-friendly for me.

Apart from being embarrassed and humiliated by his digestive condition, what is your husband doing to resolve it?
Has he kept a detailed food diary?
Listed daily symptoms linked to food intake?
Researched Ibs?
researched FODMAP?
We know you have pushed for tests which have shown that there is nothing really sinister lurking in his guts. So to put it simply:
Something doesn’t agree with him.
Find out what it is by a process of elimination.
Example: Start with the onion family.