Thank goodness there are only 2 multiplayer achievements. I personally detest mp achievements.
Pretty sure I'm not going to get the "Win all Races in the Campaign" achievement as I've never been particularly good at driving.
Nightmare sounds daunting. Probably do first playthrough on Hard to see what it's like.
For the two collectible achievements, I hope there aren't too many or at least give us the option to backtrack for them (which seems likely given the open world).
Everything else sounds manageable so far.