jeez, I hate to hear you're having this much trouble, I know it can be super frustrating. I have to wonder if the thermostat might be in backwards (I did that once I think) but it sounds more like you have some sort of blockage like you mentioned. but I just can't imagine what that blockage is. another possibility might be that the water pump gave out and is not actually pumping (a longshot might be that the pump froze at some point in the past, and tore up a belt which might explain the turd you found. and now its not pumping and thus causing the overheating.) well whatever it is I hope its not too expensive a fix.
