Looking at your diagram, it is entirely his fault, if your picture is acurate, it is clear whois at fault, as you have passed more than half way, before he turns. Therefore he should have waited until he could see it was clear. Id keep on at the insurance, dont worry about what witnesses he has, you have your own witness, so just concentrate on your own claim. And push the insurance to claim from him.
Accidents suck, when the police dont back you up. Had an accident just over 3 years ago, car and i came together, i came off a lot worse, (but thats riding bikes for you), lost the lower part of my right leg, 5% use of hands, which isnt a noticable thing, 20% memory, and a whole lot of healing. And the police said at best i could hope for was a 50/50, i got nothing at all. Lost bike £4kish lost limb (priceless), loss of earnings (again priceless), he however had his Merc replaced, and he had compensation as well, due to him having his young son witness the accident.