This needs filming as potential evidence. Throwing items at someone is also assault..and people have been convicted for it. If what you say is occurring on a regular basis then it should be easy to film - use anything. Get witnesses. Then call the police. If they try to squeeze you off the road, make sure you ride primary (aka taking the lane). Let the driver make it worse for himself, if he must, but never ride in the gutter. As mentioned, witnesses and footage are crucial. Stay safe mate, all the best.
What is the make and model of the dash cam?
I would need one too like this to show speed, date, time, position,
Can anyone help ?