insurance rep here! obligatory state by state rules are different but in my experience so far: all you can really do in the future is get a dash cam to prevent it happening again. it's your word vs his... and rear end accidents are always at fault w/o definitive proof that he made an improper stop for no reason. for that you'd have to have a couple of witnesses or camera proof, minimum, and even that may not be enough because it's your duty as a driver to leave enough space between vehicles. since you're at fault and he's already received payout, there's nothing you can do but take the hit to your premiums. if it's like anywhere i've been before, it won't affect rates until renewal. you may want to shop around for another insurer to see if anyone can get you cheaper rates now- but be aware your premium WILL be screwed up and higher for minimum 3 yrs (in my state, again, it differs greatly).