The slide stop lever tab is supposed to be long enough to reach out into the follower's cutout. A little bit of brass rubbed onto the tab isn't a problem, but if the slide stop is nudged up by contact between the bullet and the lever's tab, then it's something to examine.

S&W 3rd gen pivoting extractors can't be checked for fit in the same manner as a 1911 (meaning slipping a 230gr dummy round under the hook to see if it is dislodged by gentle shaking). That's probably why one technique is taught in the Colt armorer class and the S&WE 3rd gen class involves the use of tools/gauges to fit and check the extractor and its spring tension. The tools are used for a GO/No-Go check (bar gauge and the older flag gauge) and for checking that the spring falls within a recommended tension range (5-6 1/2 lbs on the force dial gauge for .45's).

In older .45's (645 and early 4506-ish?) there were some extractors that also had an adjustment pad on the tail for fitting the extractor. I've never run into one, myself, but we were told about them in my first armorer class.

The slide stop pin notch is for the guide rod plunger. The barrel's bottom lug surface catches against the pin's shaft to hold the slide & barrel on the frame when they're forward in battery. A tech or an armorer might simply replace a slide stop lever assembly if it exhibits a lot of unusual wear or has an unusual, noticeable "high spot" which might be causing some issue when the barrel's bottom surface is running forward against it. Dunno. Have to handle and examine the gun(s).

I've corrected a couple of feeding/functioning issues by replacing slide stop lever assemblies in new production 4566TSW's, though.

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Ret LE Firearms inst & armorer