I've only had it out twice since I fixed it, but my 99 is working just fine.
I polished the flats of the sear and hammer/striker without changing the dimensions/angles and inserted the new sear.
Works just right. Yes, it has a LONG take up, but the polishing I did makes it a smooth take-up, even if it feels long and around 6-7lbs.
I used a snap-cap to avoid damage to the FP and did all the things that had made the hammer snap forward before: slamming the lever the last 2 inches to chamber the snap-cap, 'dropping' the rifle onto its butt from about 2-3 feet, etc. No slipping off the sear now.
I didn't try dropping it from 6 feet onto concrete: I like this rifle too much.
However, I'm pretty sure it is working at least as well as it was designed to, if not a little smoother.
Everyone: thanks for the tips on the magazine. I left it alone.
I am just irritated with myself as I had found a spare firing pin and it seems I lost it around the house. I'm thinking it might have been gray binned by the little lady, thinking it was garbage [in a small plastic bag].