97 Blazer running hot/leaking coolant

97 Chevy blazer, 4.3L vortec v-6
So it is a HOT day today and I'm driving home from work air conditioner
blasting and I smell antifreeze. I notice it's running really hot,
about halfways between 210 and 260 not yet in the red. Oil pressure is
lower than normal (normal is about 2/3 on the guage) and when I lowered
rpm's pressure dropped past the half way point on the guage. I didn't
notice any power loss or change in drivability. I get home and check
things out. Coolant tank is empty, but oil looks fine. Fill up coolant
tank, run it for a while. Still gets hot and oil pressure is down from
normal. I notice that coolant is leaking from under the engine, not
anywhere near the overflow tube, radiator, or hoses. I can't really see
anything under the hood, and underneath it's dripping on the middle
right (passenger) side of the engine. I took it out again and when
idling, temp was right at 210 (still higher than normal) and when I
took it up to about 45 the temp shot right up to the point it was at
before and when I stopped again it went right back down. Seemed pretty
odd to me because I never see the temp guage move that fast.

I had the cooling system flushed about a month ago. I'll be changing
oil tomorrow so I might be able to see where the leak is coming from
better, but the drop in oil pressure really concerns me. I'll probably
check out the thermostat too. Any suggestions on what to look for/
ideas would be really appreciated.