I told him I was writing this comment and he made a massive show of a massive pout XD

Good! You should wear what he wants - if he will wear what you want him to wear.

Middle is also pretty good at sizing, she has bought clothes as presents blind and never had a problem (which understandable when looking but somehow she manages online as well).

This is easy - you just have to buy XXXL and say "It is meant to be very loose" :D

(her shirt fit me perfectly and because of the tactile issues my skin has most of the time this is fine but other times it's "too tight" even when it's not even tight)

I feel like the clothes are tight in all the wrong places - I understand the belly, but other places too. It feels like a blind tailor made my clothes, using another person's measurements.