alright, looks like the problem is bigger than i thought. i've tried a handful of other save extractors, and they can't even read the cartridge. (TWL crashes the 3ds entirely trying to read it) i've looked around and tried what i could find. cleaned the gold pins, etc. seems like there's something seriously wrong with the cartridge itself. what's weird to me is the DS still reads it as a plat cartridge. i attempted to see what i could get by dumping the cart with gm9, but as far as i could tell all that would have yielded me were two .nds files, neither of which contain save data to my knowledge. just the rom itself. i tested with a working cartridge and this was still the case.
unless i'm wrong and i AM able to retrieve save data from a .nds and/or its trim file. but it's looking like as of now getting the .sav through normal save editors isn't possible.
i'm not sure where to go from here, feeling hopeless. game's been dead for probably around a decade now. if it helps, the exact error message i get when booting is "The save data could not be accessed. Please turn the power off and reinsert the DS Game Card."