1) Using self leveling compond then subfloor is not the best way to do this. Why wont the subfloor work alone, the main floor must be pretty bad. For less cost you can get a floor sander and get rid of that uneven floor.
2)Pergo has an allowance of 3/16 of an inch in a 10ft radius, or else the floor makes like a trampoline and the tongue and groove will fail in time.
3)Dampness is a problem with pergo, the rule is if there is a crawl space you need a vapor barrier.
4)Self leveling compound is self leveling, so if your doorway is in the center of the house and the floor dips that way (say an inch) you will have a 1 inch raised height in the doorway.
Self leveling compound is not the best solution. Rent a sander.