As Millsy says you could probably do it given your background of running and lasting a twenty miler but you would have to be discpilined in your pace. Why not just enjoy the run without having any pressure timewise. You could even take in the sights that would normally just be a blur to you!
Lastly I know no law requiring him to delete the video on his phone. It is also likely to have recorded the way he acted towards you. You should make contact with the officers to see who they believe was at fault which hopefully will put you at ease.
Without a photo of the location it is impossible to come to a conclusion. In terms of fault it would ordinarily depend upon who was 'on the junction' first: if the pedestrian then the driver has the responsibility to wait and vice versa. As the driver was alone there is only one witness to declare he was in the junction first (assuming he does) so without any other credible independent witness there would be insufficient evidence to prosecute. It seems as if his behaviour post incident placed you in a state of fear and alarm which in Scotland would consitute a common law crime. you would appear to have witnesses who would corroborate this.
However, as a road accident occurred involving third party injury he was in his rights to request your details.
Sorry to hear of your problem. I went to physio with knee pain. She said my knee was out of alignment due tand that one of the quad muscles which goes from top right to left of knee had effectively 'switched off'. I had been able to run on the treadmill by having it at a 2 degree gradient. This meant that the knee didnt have to fully extend (apparently) She gave me two exercises to do. The first was sitting down with affected leg straight out with a rolled up towel under the knee and pulling your foot back towards you for 20 seconds (10 reps). Another exercise was standing on affected leg only (no shoes) and balancing on toes for 10 seconds (10 reps) I did these faithfully
I have also done leg presses at my local gym to protect the knee by strengthening the muscles around it. My knee is not perfect but interestingly the faster I run the easier it is and I am able to do all the sessions I have planned.
My experience may be different to yours and of course feel free to ignore but if nothing else you know you are not alone in your frustration! Hopefully you will soon be back running.