You are enabling him to continue to be reckless and disrespectful with the responsibility of the car by not insisting he take responsibility for his actions. There are alot of ways to go about it... but you need to do something.
My recommendation is to add up everything (speeding tix, fixing the car, increase in car insurance, etc.) and decide what you'd like him to pay back. I recommend ALL... but you need to do what you feel is right. I would then sit down with him... show him the math and ASK HIM what he thinks should happen. He may actually have a good/fair idea. If NOT, tell him what you think is fair...
my first thought, is to put him on a payment plan and if he misses a payment or is late.. NO CAR PRIVELEGES until he pays it. For example, the 15th of every month (or line it up with when he gets a paycheck) he owes X amount of money. Just like in the real world... there are consequences when we are late with bills, etc. He can learn this now.
At this age, I believe LOGICAL CONSEQUENCES very important. He's irresponsible with the car, HE pays for whatever damages and NO CAR for X amount of time. He's late for school... he has to serve whatever discipline they dish out. Don't SAVE him from these things, it will only make him weak later.
Also, be sure you are showing him LOVE LOVE LOVE... i know that's hard with teenagers... but even just buying his favorite snack food or something simple like that to show you were thinking of him.
And, did you ever apologize for the "laughing at him" that you mentioned? If not, it could probably be very healing if you did...
It seems like you're getting all kinds of suggestions... so go with your heart and what seems right. But, SOMETHING NEEDS TO BE DONE. It's obvious that you agree, or you wouldn't have posted on here. Don't listen to your friends who tell you that he's a good kid and not to do anything. He may be a good kid, but you can help him be EVEN BETTER by teaching him there are real consequences for his actions.
ALSO, in regards to him looking at you like he'll go hurt himself. I hate to say it... but wouldn't you rather this happen under your roof with you there to help him learn to deal with hard things that WILL HAPPEN in life? OR would you rather wait until he's 25 on his own and has to deal with a late car payment/bill... and then hurts himself with noone immediately there to help him deal with it? Your job is to prepare him to survive in the real world and be strong and confident on his own... this is just ONE of many lessons in the process.
Also, your younger kids can learn through what he learns...
A book that I really like that deals with some of these issues is: Raising Great Kids: Parenting with Grace and Truth, by Cloud and Townsend. Be warned, it is faith based...
GOOD LUCK please let us know how it goes...
HTH
darci
p.s. the OP with the ideas about switching insurance/ getting him his own car or at least own insurance were good ideas to at least consider... but don't forget her should OWN UP to what has already occurred.