Hi, GTO. The spring-loaded sear levers originated commercially with the late MkII and all MkIII pistols as it's required to make the lever double as the firing pin safety. They were absent prior to that.
To keep from buggering up the nut, I just take the hammer and strut assembly out of the gun and then push the strut down between a vise that has its jaws opened enough to let the strut, but not the spring pass. Slip out the pin below the nut and unscrew. Just the reverse to reassemble. The paint on the lower part of the spring is there; I don't know what it signifies, but suspect it lets FN know poundage in the event that they had more than one strength spring out there.
That was just a guess.
The safety on my BHP is a factory extended safety as on the MkIII. I've removed the right side as I don't care for ambis; they get in my way with the BHP. I polished the feed ramp and added checkered, black Spegel delrin stocks. The gun has not been shot much at all and I actually wasted my time in detailing, but cleaned all internal parts and now KNOW that the pistol's clean and OK, internally. I bobbed the hammer at the second lateral serration and reshaped and reblued as is my custom. The trigger's quite good and quite crisp on this pistol and since I won't be getting rid of it, assuming it works and groups, I didn't try just replacing sears and hammers, hoping for a lucky, "good," combination. The safety does NOT allow any movement of the sear when engaged as is too often the case with some HPs.
Hopefully, I'll get to shoot it soon...like tomorrow.
I see javelina in this little gem's future.
Best.