I need some help figuring out why my 1996 Acura 2.5TL (250k miles) is overheating.

Brief history:
Bought in November, ran great during test drive and for a few weeks afterwards.
Replaced the blower motor.
Replaced battery, alternator, belts, and spark plugs/wires.
Replaced the crankshaft pulley.

Not long after the crankshaft pulley was replaced (I didn't do that part myself), is when it began overheating. I'm not sure if there's any relation there or not.

When I first noticed it overheating, I was idling in a drive thru and out of nowhere a bunch of white steam/smoke started coming from under the dash (and kinda through the vents, but mainly under the dash on the driver's side) with a hissing sound. It was the antifreeze evaporating. At first I thought maybe a bad heater core but now I'm not so sure. I think maybe what happened was that I wasn't paying attention to the temp while I was waiting in the drive thru and it got too hot, pressure built up, etc. Although one of the hoses/pipes going to the heater core (on the drivers side, kind of under the radio) was leaking, but I fixed that yesterday and it still overheats. What's interesting is that after I fixed the leak, I drove the car around a bit and the temp was steady for a few minutes, then out of nowhere it shot up.

Today I tried opening the valve on the thermostat and fed a little antifreeze directly into the radiator, hoping maybe the cause of the overheating now was just due to an air pocket not letting coolant through. But either I didn't do it right or that's not the problem because it seemed to have no effect.

I also noticed today that the radiator fans aren't coming on, or at least not when I let the car idle in my driveway. I'm not sure how/when exactly they are supposed to operate. But I jumped the relay on one of the fans and the fan worked. So then I jumped the B switch on the thermostat and the fans did not turn on after a minute, but the relay also gets power and is grounded. All the fuses look good too.

With that said, I'm not sure how to continue. I'm hoping it's just the thermostat and not the heater core. Or hopefully something as simple as flushing out the radiator? I don't know much about cars other than what I've researched on the problem so far... so any help would be great!!!

 

It really sounds like the thermostat?