Did you rotate the engine before trying to move the valve. If the cam is still in contact the valve won't move. IE be sure the cylinder is on TDC of the compression stroke ~ then the valve should be easy to get unstuck.
Your plan of attack is pretty good, but be very careful as you are playing with many separate systems that work together.
While your at it I would recommend new fuel lines from the "tank" and adding a cheap fuel pressure gage which can be priceless when trouble-shooting fuel related issues.
Dave Neptune
