--there's a 100 when lit special in the middle, but it always seems to give 100pts-- Do you mean it is still giving only 100 points even when it's lit, or it is never lighting to begin with when you complete the correct card sequences?

On the screwy scoring, are you having similar sticky reel problems during reset, i.e. do any of them esp. the 100 reel seem to be skipping advances and taking longer to get to zero? I could see maybe if the 100 reel is sticky, it will be stickiest at position '9', and thus it could end up giving extra pulses to the 1,000 reel (where you went from 1500 pts to 3500). Since you say they look like they are 'trying to turn' that sounds like gunk/dirt/misadjusted switches in the reel(s) but only if it's messing up the same during reset and during single scoring like 10, 100 etc.