wait wait wait… i’m guessing 100 grams is alot? i’m not familar with metric… sorry.
what is his diet, everything that he gets on a daily/weekly basis and amounts? he does not get ANY pellets AT ALL? how do you know he get a stomach-ache? does he have teeth problems or something that is preventing him from being able to eat them. you want to be careful with just increasing calorie-rich food b/c you don’t want to cause other issues. remind me, how old is he and is he neutered yet? when was he neutered?
we had an interesting thread awhile back about bunny diets with no pellets. and if it was better to feed a completely natural diet (veggies and hay only). the conclusion was that a limited amount of high-quality pellets helps to fill in all of the little nutritional gaps that are missed by the veggies.
will you be returning to your flat after your flatmate is hauled off? i wonder if he will resume his normal habits in familiar territory? (your bunny, not your flatmate ;o)