A "crack" that has an elevation difference of 1" per side is a structural failure and it's going to telegraph through to the final floor surface regardless of the underlayment. If mud jacking is out of the budget and you're confident the foundation has stopped settling unevenly, then grind & self level. A walk behind floor grinder can be rented for $200 and then use a hand grinder to get the edges or corners. Carbide flail type walk behind floor grinders are 3x faster at removing bulk than the horizontal rotary diamond disc grinders. After knocking down the bulk elevation differences and thoroughly cleaning, move on to self leveling. Install a bulkhead and ball valve towards the bottom of a heavy duty 30 gallon trash can to dispense the self leveling compound. Put the trash can on a flat furniture dolly, mix the mud, crack the valve open and wheel it L-R , wall to wall in a "Z" pattern similar to applying paint with a roller. Have a helper using the notched side of an asphalt lute to distribute the compound as you go. But, I'd find out why the foundation cracked before I looked at installing new flooring.......
