I can understand how he is feeling to an extent.Some people do mourn food & its probably hard for him to see what you & the kids can eat & he cant.Those feelings will pass with time(hopefully),there are things I see that I want to eat after 18mo and I dont & honestly I get a bit frusterated,then I think about it and know I made a good decision not to eat whatever it is.
So basically try not to have the "bad stuff" in the house since its not healthy for anyone.Since it sounds like his journey has just begun,it will level off with time food wont be such a focus.
It might be rough for a bit but it will be ok
Hang in there!! Were here for ya!