The Backhand Brake

Plant the front foot perpendicular to the throw direction when throwing a backhand.

Here's something that may help with your backhand.

When you plant your front foot in preparation for throwing/releasing a backhand, take a look at how you're planting your foot.

Ideally, your front foot will initially plant itself perpendicular to the direction of your throw. Doing so provides a sort of "brake"; it gives you a leverage point to pull against.

If you're frequently rounding or pulling your backhand, it may be because you're stepping with your lead foot pointed directly into the direction of the throw. That can cause you to swing open (and pull the throw to the side).

Take a look at this clip of Calvin Heimburg throwing a backhand. Notice how his front foot plants perpendicular to his throwing direction. As he throws and releases, the foot starts to spin and open up (due to all of his torque and momentum). But at the start of his foot plant, he's essentially stomping down perpendicularly across his throwing line.

The feeling you may get from that foot plant is of a "brake." It feels like you're bracing against something. And that's what you want to pull from, to concentrate your power.

See if this helps. Keep throwing.