I'll dig the armourers manual out and try to come up with some suggestions for the trigger.
Weaker hammer spring looks to be all you can do, the disconnector spring doesn't seem to contribute to the recocking force like it does in an AR
I would buy 2 hammer springs, cut one down till it's starting to light strike, then cut the second one down not so far as the first. Keep the original as a spare.
I would be cautious about removing any coils from the mainspring. You are messing with the breech timing and can run into problems with feeding the first round when cocking manually.