I would do my best to concentrate on the fact(s) that:

(1) You and your brother are only coming together for this no-win event.

(2) Your father will die soon and probably does not see/understand any of what is going on now and probably would not change how he responded or felt about it even if he did. He's not suddenly going to beome lucid, sit up, and annouce, "LMo is the best child in the land!"

That being so, do you want/will you have a different relationship with your brother afterwards than you did before or would have had if your father were not dying?

You will go your 7 hours away and he'll go his 2 and. . .? What do you want from this whole encounter/experience? If it is so "against" you and painful, I would leave and maybe come back for the funeral, maybe not, depending on whether you want to support your stepmother or not?