sam2- the steipler in a letter in back of hilchos chag bchag writes that a choleh can be somech on the avvnei nezer.
old man- The Chazon ish at the end of kuntreis hashiurim is very clear that the shiur kdei achilas pras is a set time and is not dependent on the food you are eating. His main raya is from eiruvin 4a ?? ????? ???? ????? ??? ?? ????? ??? ?? ??????. However the minchas chinuch in hilchos erev yom kippur brings up a tzad that it goes by each food.