Operator very rough to open

Sounds like you either need a new operator or a new hinge. A good way to test that is to disconnect the operator from the sash and try to open the window by hand. If it's still rough, then you need a hinge. See our 36-048.

If it opens smoothly, though, then the operator is the culprit. We have a couple that may replace yours, but in order to confirm I'd need you to remove the operator from the window and show me a picture of it separately. I especially want to see the bearing  at the end of the arm.