93 Protege.. Cold Misfire/Engine stumble at 2000-2500rpm..

hey ive been noticing this problem over the last week and a bit.. i always warm up the car for 2-3 mins now to avoid it, but also i am noticing that after driving the car for a while upon re-starting it starts "off" will drop down really low like 400 and shake and seem to be misfiring in at least one cylinder, then recover back to spec idle the car has been vibrating at idle below 1000rpm for a while but this just started happening. id drives fine.. sometimes get the smell of fuel and sometimes a sulphurish smell too.. and theres a creak when i take off and when i put the AT into drive, and a thump into reverse.
theres more probs it seems that i really wanna deal with.. and they seem to be intermittent at times..
time for a new car i know.. but I really wanted to sell this one and get some ok value for it it cant be missing and idling rough and there is a bad driveshaft bearing or the caliper in the left wheel might be seizing up??

The first two items I would look at are the transmission fluid and catalytic converter.

For vibration below 1000RPM, I'm going to assume you have an automatic transmission (by the way described going into reverse). Whats the condition of the transmission fluid?

What's the condition of your catalytic converter? A catalytic converter with mangled substrate can cause a sulfer smell and decrease performance.

Oh Oh Big Help

the tranny fluid is fine and i had a cat put in about 11k ago.. yes it is an automatic..

NOW theres a big problem and I am almost sure this is why it was missing..

Think i have a blown head gasket or major head damage.. there is milky white residue in the oil cap and under the pcv valve.. there is way too much positive crankcase pressure as well.. . are these two related?? when i take off the oil cap/pcv valve white smoke is coming from the valve head.. and disappearing.. 99% sure theres coolant in the engine! this would explain why its missing when cold, and why it starts weird when warm as well.. theres coolant in the cylinders..

i can get a buddy to do a hg job for change comparing to what a shop would charge.. but hes not so sure why theres so much PC pressure, and says he wouldnt be surprised its more than just a blown hg.

help please.