I am not sure that you can really influence your stepfather in this. I remember my FIL saying that he knew his wife was dying when no-one tried to make her eat - but he felt able to accept this.
You are stuck in the middle here - you have your own grief to contend with and it is hard to have to support another person, who is trying to deny the reality, which I am sure you wish were possible for you.
I wish you all strength in the time to come.
Air fryer - combi microwave - oven? Help!
Gary Glitter programme Tuesday