Attach the ball joint to something heavy. Might bolt it to a trailer hitch on a vehicle. I use the attachment posts on a plow.Then try working the actuator back and forth by hand. An extension pipe on the actuator will give more leverage, but be careful that you don't break the actuator.
Either it will break loose.... wring the end off the actuator.... or pick up whatever you have it attached to. (If you pick up a truck....I ain't gonna mess with you.lol)
I tried using a torch to loosen the rod in an old superjack. It loosened real nice... but melted the teflon acme nut inside. Ooops! No real loss since I discovered the threads were corroded away after I cut it open.