The half cock notch in the hammer needs to be re-ground deeper & the sear angle corrected at the same time. Easy to do, an hour with an Arkansas stone and the hammer in a vice.
Unfortunatly your headspace problem requires a bit more work than just changing the load. By increasing the load, all you will do is increase the beating your action internals will be taking. True, the primers will be embedded back in the cases but the headspace is still there.
Let's start with how much measured primer protrusion is there. In modern high pressure guns very little head space will cause brass splitting or rupturing...not the case with some of the older rimmed cartridges that only produce 25,000 lbs or so, the brass will still do its job. Personaly I don't get worried about headspace in these old girls until I can measure at least 15 thou primer protrusion after firing an empty case with just a new primer in it, no bullet or powder, just the primer. At 10-15 thou I always keep the loads at the bottom end of the scale (as you are using now) for that particular caliber.
If the headspace is excessive in your gun and needs to be fixed, you have two choises...re-line or turn in one full turn to index the barrel dovetails &re-chamber. Both have their benefits/drawbacks to be considered.
Relining keeps your original barrel dovetails all lined up with the mag tube & forestock mount but in the case of the 38-55, it needs to be securely locked in place.
You say the bore is very good yet, so option # 2 is viable as well. It requires the barrel to be cut & turned in one full turn and re-chambered with correct headspace. Unfortunately with this method, the mag tube and forestock must be shortened a corresponding amount to match dovetail cuts, changing the original spec's of the old gun.
