Chugging/irratic idle

I have a 1995 Civic DX, 1.5, auto tranny, 2wd, 164,000 miles. My civic is a bit of a dog. I have had a small leak in my exhaust just before my muffler, and have had some oil consumption.
I had the head gasket replaced in the last 6,000 miles.
I was driving up a slight hill, I depressed the gas to engage the passing gear, when I noticed a difference in not only sound, but power. It sounded like a riding mower, with much less of a pull.
I drove home, and after the exhaust cooled down, I noticed a break in my exhaust, just before the resonator. I tried to clamp it, which did not help. It idles really low in gear, at stops I put it in neuteral to avoid stalling. It chugs apon acceleration, until the rpms get higher, it seems to run fine.
There are now "check engine" lights on. I had the cap/rotor replaced about 3,000 miles ago. I just replaced the plugs today. 3 were gray, one was oily. I'm wondering if I cracked a ring, or worse? Any help would be greatly appreciated!