I say this as well! I like the 09+ retros better then the OEM 14's, when painted black though. And a shroud that stands out with amber halo behind it.

DUCE- You started on the wrong edge!
No I'm just kidding!!!

My first light looked like that also. I used 2 different sized flat bladed screwdrivers. A small bladed one like the one you were probably using, and the other one was the biggest I had around 1/2" blade. I started like you did until I could get the 1/2" one in there and it makes a huge difference.
The damage on your light can be cleaned up with a heat gun and just forming the plastic back. You shouldn't get that all the way around.
I say keep trying it. You only have a few minutes after the light is removed from the oven to get it started then put it back in. Once you're able to use the big screwdriver it's way easier. I put a big piece of cardboard on the counter and opened them up in the kitchen. I then went to the garage and removed the perma seal that was left in the channel with a heat gun and small screwdriver.