Even if you do manage to claim through your insurance you’ll still take a hit on future policy costs. The guy sounds like a complete liability and, friendly with senior club members or not, given he’s got history I think he should be footing at least part of the bill here.
If other senior club members are prepared to back him then either they’re out of order and should deal with this properly, or there’s more to this than just your side of the story (no offence).
Assuming there’s not more to this, I’d be having a serious word with senior club members and refusing to ride with him. Even if it means joining a slower group I’d just make a point of it and make sure people know why.
Not the best option, but if there’s another club local (ish) I might even be tempted to flounce off and join them.