Elksniper,
I don’t want to sound too pessimistic, but from the pipe wrench witness marks on the pin in the picture, it appears the pin is soft and likely significantly galled in the bosses. Therefore, even if you can get to the backside to pound on it, you will take the risk of swelling the pin by hammering on it and make matters worse.
Since you are asking for suggestions and are already considering welding a nut on, can you get your hands on a hollow ram hydraulic cylinder and hand pump? My local hydraulic shop has let me borrow rams in the past, or possibly a good equipment rental business to rent one along with a hand pump?
If so, get a piece of good B7 all-thread rod (not the cheap all thread rod at the lumber yard) and weld a piece on to the pin. Then you should be able to pull the pin with the cylinder. Sometimes a little heat on the bosses also helps to break things loose.
Here is an example video. He is using an air actuated pump, but I have always used just a plain 10000 psi hand pump.
www.youtube.com/watch?v=Pq9G73_o7ug
This may be overkill if you think you can get the pin to move with a nut welded on, but I am guessing that adding a nut won’t change things unless the heat from the welding frees things up.
Again just suggestions for your consideration.
Good luck, and as Alrman stated, Think Safety!