Eccentric bolt won't budge

[1983/300CD]

I'm attempting an alignment.

Measuring the caster using the 20 degree turn method and spinning the guide rod, I've adjusted the caster to:
Left side : 4.6 (in) + 3.4 (out) = 8 deg.
Right side: 3.7 (in) + 4.4 (out) = 8.1 deg.

Now checking camber with wheels straight ahead, I get:
(Left) 1.5 degree negative
(Right) .5 degree negative

So, I set about loosening the eccentric bolt nut. 24mm socket on the breaker bar should do it, but it won't move. I even tried putting the jack under the breaker bar and started raising the car with the eccentric bolt nut. It isn't rusted or exceptionally dirty. Is there some trick to this other than giving $75 to a "professional"?