OK, sounds like you're going in the right direction w/ the jam nut (clock-wise toward the receiver). However, when the jam nut is doing its job, it is more inclined to actually have that FF tube travel with it vs. breaking free from it (resulting only in tightening the whole works towards the receiver). Having that jam nut and the ff tube being torqued in opposite directions simultaneously is the key.
I think if you can find a buddy to help you out you'll get this thing off - the one with the stronger hands should take the free-float (must wear gloves, too). If you end up needing more torque than a pair of gloved hands, you can cut a strip of bath towel the width of the tube, tie it in a loop, wrap the loop around the ff tube a few times, and use a breaker bar with plenty of towel to cushion between the breaker bar and the tube. This would risk damage to your tube and too much torque could damage your receiver so I'd use this as a last resort.
I have removed that tube from that rifle recently - there was no thread locking compound on this particular unit. I believe YHM only recommends use of a thread locking compound on the end-cap.