Don't quite know what to say, I did mine a couple of winters ago, it came right out, bushings tapped right out too. Had everything supported like mentioned above so no weight on the pivot to speak of. Dumb question to ask, u sure you got the bolt that goes throught the shaft on the opposite end as the nut out? Hard to believe that with an almost 1.5" nut you can't get enough leverage to spin that shaft to free it.
I would soak it a few times with penetrating oil and let it set a day or two. Last resort get a few sawzall blades and slip the blad between the frame and ears of that yoke and cut it into three pieces. Would seem that would release any binding, and tap out the pieces.
Stumper63