I did all of these things, but after cooling my pie still wept. What am I doing wrong?

There could be a few reasons. The sugar may not have completely dissolved into the egg. Try to mix sugar and eggs at a slower speed and make sure it feels smooth and not grainy. You want to use the least amount of mixing motion to ensure the bubbles in the eggs do not shrink. Add meringue when the filling is hot to form a stronger bond and seal, and make sure you spread over the entirety of the filling! You could try adding something acidic to ensure bubbles are completely formed. Lemon meringue has a relativity short lived storage life; it will only last about 2 - 3 days baking, and weeping is expected after this.