Alright, a very quick preliminary;
My 14-day remaining score was 659,115 and was well off on a couple things. My final score is 820,849.
So not only can some scores go over, they can go *way the hell over.* Also got literally every achievement for it (ugh), with a bunch of insane json edits active so there is definitely no checking.
...
Having every mech should be worth more than 76,380, I'm still missing one standard mech and at least one SLDF, and so also missing the chassis completion.
All 10 reputations are capped + or - 100, so Arano and Aurigan reputations do not count, and it is capping those at 100. The 40,000 for four positive and four negative reputations are right, but 50,000 for faction completion does go up an extra 30,000. But getting four at max without Arano counting means you can't have more than two alliances.
Both mechwarrior experience and C-bills go over. C-bills I'm almost at the ~2 billion point where it rolls over. Mechwarriors I'm not sure if/where they roll over but I have four that are over 400k experience from a single edited mission (where ~20k points came from, so it appears that all of that extra counts) along with a dozen other straight-10 pilots and the rest of the barracks full of pilots who have capped out on the simulators... but I don't think c-bills of that magnitude are legitimately possible even on the easiest settings.
My post-game score screen shows all the correct actual points for categories that go beyond the "caps." It's sort of silly that during the game they appear as caps when they really are not.
At some point resuming my normal game I'll get a real finish and hopefully see if the contracts score can go over as well. If a "point" of difficulty is each half-skull, that is another one that potentially can go quite a bit over as well, my normal save has ~250 days left and that'd only require about 50 more 4.5/5 skull missions.
Also a thought; Kerensky might not have been intended to be achieved until Urban Warfare, or even the third DLC is out. With the spoiler mechs and extra mechs from Flashpoint counting to the score, the later DLCs might be intended to add more points.