I got out first and tried to move over so my grandpa would have room
Why do all that for your Grandpa?
I'm trying to spare his life
It is nice that you care for your grandfather and wanted to make his life better. It is expected that we care for and respect our elderly relatives.
I tried to do something nice for him and all he did was cut me off and almost killed me.
Even if someone doesn't respond kindly, its better to be nice to someone than treat them poorly. You'll be able to live knowing that you tried to be the better person.