Almost all of people that will buy your car don't care if it's had the fender fixed, to a private seller it won't matter and to a dealer their customers won't care in this situation, the only consequence or repairing it through insurance is that when you trade it in you may get an excuse that it has been repaired and your trade in offer will be lowered, this is BS just point that fact out against their lowered offer and they will forget about it. I have a lot of skill when it comes to negotiating car deals and I've bought 40 classic, exotic and other cars for a small fee as a job on the side. What matter in the end (and to me when I look for a vehicle to buy) is that it hasn't had repeated or serious accidents.

I'm not sure what you mean by the touch up affecting the overall paint job.

There's no reason in my experience not to file an insurance claim in the long run. The turn around for you car should be 48 hours.

Hope that helps.