Congrats on snagging the car, but sad to hear about your mom. I've never had trouble with the seats in any of mine, but have heard occasionally about broken slides, so you may want to search that. You done did good work on the vid and laying out the problem, and hopefully gives worthy payoff with the exact fix.
There's a strong possibility repair will require (or at least be made 1000 times easier by) yanking the seat. If this ain't your daily driver (yet) then you'll be able to do some power testing and checking things faster - for a headstart when that real smart guy posts exactly what's wrong.
\'96SS SOB: SSRI, Herter Tune, Tri-Y II, , 3000 Edge, F/HO bars, METCO extendeds with CV MMC, Bilsteins, currently Vredestein Ultrac Sessanta (315/35 rear). Finally, wait for it... LT-4 knock module!
\'96FWB BUW-Butt Ugly White: PCMPerformance tune, HDFA w/ swissed filter, 1/2 SLP s.s. catback with H- and Flow Super 50s, oem opti rebuilt 3 times, SS Bars, METCO LCA, Airlift 1000, Monroe SS, PowerTrax No-Slip, CTS wheels with +1 rubber. Finally, yes again... LT-4 knock module!