have you considered just making it so friends don't get reset at death? i know it sounds kind of sacrilegious to what a multiplier is supposed to be, but it would be the simplest fix and (imo) wouldn't ruin scoring, it would just make one death less of a disaster. would also have the added benefit of making it easier to tell when your next extra life is after dying.
that'll be my only suggestion because i know backseat game designing can be annoying. i just think this game rocks and could be a super fun and rewarding thing to put a lot of time into with a few minor tweaks. : )