S10 AC schrader valve

I have been working on the AC on my 96 S10 and i think my low side schrader valve is leaking. I got a core removal tool. Took it out, and put it back in. It seemed to go in a little too far. Should the AC
schraders screw in just far enough to cover the threads, or is there a stop in the fitting they hit and you adjust to?
Also, the high side fitting seems to have a rubber ball in it. Are these removable?

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