I had a similar problem many many many many years ago with my 72 Corolla when i modded the engine (who would do that to a 72 Corolla? me!) The engine wasnt seized, but I scored the crank bearings and ripped up the end bearing (it was knocking... like someone tapping it with a crescent wrench). As for powering out and sputtering.. that could be fuel pump or filter. Or.. just low fuel (going for best case scenario)... apparently Supras dont touch the bottom of the tank, so you can run out prematurely, but still have fuel.
As for the squeaking though.. thats scary. Hope that you didnt do internal damage.. a little is a lot. Perhaps its time for you to really mod the engine ($$$).
When you boost the engine.. does the starter make a click-click-click sound? If so, it is too low powered to engage. If it makes no sound, gonna guess the engine is totally seized. If the battery is dead and you boost it properly ... it wont start (what I mean is.. if the battery is dead to the point it will not hold a charge at all). You have to jump it post to post rather than use the engine as a ground. This is dangerous... as that is how you explode batteries, but I have done it carefully before, its just very bad practice... so.. saying that.. try using a battery out of a vehicle that works, or test your battery (maintenance free batteries can dry up.. then they smell like sulfur)
Crossing my fingies for you!
