Will he take a bottle and can you express?
Just thinking that if you can have some frozen breast milk ready you could have the odd bit of dairy and use frozen expressed milk for 24 hours.
Yes I know not everyone can, I know not all babies will take a bottle, I know some babies don't like to change etc etc.
I agree with the others that it is unlikely to be lactose intolerance in your baby, it is incredibly rare in all babies, even in countries where 90% of adults are lactose intolerant.
Also yoghurt and cheese have less lactose than milk so shouldn't create a reaction.
Not saying your baby didn't react to the yoghurt, just that it is probably something else in it.
I think the main thing is to keep your diet as healthy as you can (and you can do that without chocolate and cheese) and your baby is feeding and not having symptoms.
Obviously do go to your Dr but you seem to have found something that works.