Other Rainson Edge regulator leak madness

My Rainson Edge has a leak, of about 15 bar/day, and it turns out that it is in the regulator. After removing it, this part of the regulator appears damaged.

probe_50pct.jpg


(Taken by the James Webb Space Telescope)

That line from the light goes right through one nick, and there is another nick towards the bottom. My questions are:

Q: Is this a problem? I assume nicks in brass near o-rings are Bad, but maybe not.

Q: Assuming they're not, according to the diagram in the manual (which BTW sucks pretty hard) there is another o-ring on the other side of the Belleville washers that may be leaking. I'm not sure how to get that open. I have this:

Regulator_13.jpg


I assume there's a really small set of snap ring pliers or a pin spanner that will fit those holes. In real life those are about 1mm.

Any advice? Thanks!