Just a note, one thing that might help in the future is to cut the panel of wood down to just above finished dimensions prior to inletting the lock. This way you don't have to inlet through all the extra wood and it is easier to get a nice fit this way.
A bit of information regarding file marks, finish etc. on spring. I have seen some very coarsely filed original springs, sometimes at an angle almost perpendicular to the axis of the spring. Also, even on the highest quality guns, spring finish is somewhat less than might be expected from todays perspective. For example on a French flintlock by Thuraine, the internals and external parts are extremely well finished, but the mainspring still shows relatively coarse file marks at an angle to the axis of the spring. There is absolutely no doubt it is original to the lock. What I'm getting at is that I believe the need for a finely finished spring and the tendency for breakage has been overplayed in recent times. If you have the chance, start looking at original examples and I think you will probably agree. But with that said, I usually finish a spring out fairly fine. Just can't help it I guess.
Jim