Window A/C

If its level, I would not worry too much. If it was tilting towards the window, then I would say it could be a problem. Can't you put a wood shim underneath the front of the A/C to get the tilt?

More information please: just how does the window force the unit level?

Guessing, but perhaps you need to add height to the inside stool/sill (screw down an appropriate sized piece or two of wood to the stool) to clear an outside storm window?

A package of door shims from the local hardware store will solve the issue.

If the window sill runs right up to the window bottom when the window is closed, then the air conditioner should be sitting properly when the bottom of the a/c is up against the back of the window sill and the top of the a/c is being held by the bottom of the window.

Are you sure it's level?

You left out the storm window. With many triple track storm windows, the bottom cross member may sit a bit higher that the sill causing the AC to tilt inward a bit. In that case, the sill must be shimmed.