1991 civic, rough idle, jumpy rpm, extreme coolant leak..

[Zoe503]

1993 Honda Civic 4 cyl/2.3L Front Wheel Drive Automatic 173000 miles

My car had a slow oil leak when I got it, no big deal as long as I keep enough oil in it, I've heard many many civics burn or leak oil. About a month ago I was driving and noticed my car overheating, there was no antifreeze, put some in and problem solved.. for about 2 weeks. it started overheating again, more antifreeze. This happened more and more often, but being the Christmas season I didn't have enough to fix it, so I just made sure it always had enough coolant. Last night I noticed it was idling rough, added a whole lot of coolant. It also seemed hesitant to accelerate from a stop without giving it a fair amount of gas. Checked the oil and antifreeze they were okay. Went to a movie and when I came out and started my car, the RPM's in neutral and park were jumping from 1000-2000, up and down, changing every second. In drive it idled very rough and jerked forward in surges every second when you took your foot off the brake. It started overheating again after a few minutes, and took a full jug of antifreeze.. this stopped the jumping rpms, but the acceleration was worse than before. I couldnt seem to get out of 1st gear, maybe it was 2nd, without almost flooring it. The full jug of coolant lasted only about 3 or 4 minutes, and the rpms were back to jumping and it was overheating. As well, black smoke would puff out of my exhaust in little bursts every couple seconds, and when it did this there was a bit of a popping noise seemed to come from the left side of the car, almost underneath. this only lasted a few minutes and ceased, though the black smoke continued. We couldn't make it 1 block without it overheating and we had no antifreeze, so I parked it and had it towed. Of course, no antifreeze meant no heat and this was in -30 Celcius (-22F) between 230-400am. Headgasket, cracked cylinder head, or something else?