1989 Civic crankshaft pulley problem

I have a 89 Honda Civic, standard hatchback, which is a manual transmission, with 84,000 miles. Recently my car has been starting to run hotter, then normal, then hotter. My car was also taking a long time o warm up yet was blowing cold car when it was warmed up. This fluctuates under normal driving conditions. At first, I thought it was just the thermostat. However, when I noticed I was also low on coolant, and put more in, I saw that it was leaking out by where my water pump is located. Seeing how I must remove the timing belt to get to the water pump, I started to do this. However, I cannot get the nut off that holds the crankshaft pulley on. I have tried everything up to a 500 foot pound impact wrench. I have also tried wedging a screwdriver in the teeth of the flywheel, and trying to take off the nut with a socket and a breaker bar. However, the pressure of the flywheel and the screwdriver creaked the case, and the nut still hasn't budged. I am considering trying to sell the car as is because I cannot make any forward progress it seems. Help will be greatly appricated.