You have a defence in that you had to take evasive action to avoid a collision. Write to the Procurator Fiscal and explain this. If they prosecute nonetheless you will have to plead not guilty and proceed to a trial. I doubt they will take it further if you give them a defence. The police can only go through the motions and don't have the ability to make decisions outwith that. The procurator fiscal is the one who can make a decision. Happy to discuss further. I hope that helps. Please leave a positive rating so that I am credited for my time.
The police will generally just give you the footage from just before the incident. I am not aware of any limit on the length of film. However if the vehicle is under the speed limit and then has to speed up to avoid a collision you would have a pretty strong defence. The 10% plus 2 policy is simply to deal with tolerances in different car speedometers. Generally they won't prosecute within that tolerance as you're likely to be within the limit. Your main issue here is that you had to avoid a collision and if the police are putting that in their report it may be that the PF will take a view not to prosecute.