Army - I agree with Jim here - use something shorter. Perhaps 1-1/4" in length. Make sure you are hitting some structure with your screws as well. If structure doesn't exist where you want to mount the TV, consider mounting a piece of plywood on the wall, to some structure, then mount the TV mount to the plywood.
You may want to call Heartland today (877-262-8032) to see if they can tell you if there's any backer in the wall. If there is, you can skip the plywood step.