Hi Terry,First and foremost, I'm glad to hear you're ok! So sorry you had to go through that. I've been in a life threatening wreck before, and I know how terrifying it can be - both in the moment and afterwards.
Perhaps a bit off topic, but I encourage you to get checked out by a doctor twice. Once sometime soon after the accident and once one to two months later. Some damage shows up immediately; other things show up in time.
I use a privacy screen to cover my tools in the trunk. The Kia I drive didn't come with it so I had to order one. It was worth the $80 extra. Not only does it keep prying eyes off my tools, I *think* it would keep everything from flying all over in the event of an accident.
A friend of mine built a wooden platform for the back of his car and has permanently attached it I think. He stores his tools under it and sometimes an action of top of it.
Either option might be something you could check into. Good luck!