Don't jerk the wench but use leverage and a smooth steady force. I use a pipe over my ratchet. The higher your hand the more even force you can give.
Yeah impacts are great, if you got an air compressor. I don't.
One way or another its coming out. If needed a new timing case cover is needed, Look on ebay or buy new form Summit, etc. Be like $100
If you have a cut off wheel and your pretty sure your at the break limit and its frozen stiff. A quick cut above the bolt would let a screwdriver in to pound-spread the metal and you could spray more oil in. Should go then, new cover is then needed.