It looks like you got one cone washer off, but there are three more in place. When I removed my steering arm I had to break those washers loose before the arm would come loose. IIRC, I used an old wood chisel and penetrating oil to get under the flange of the cone washers and break them loose. Once I had a little space under the flange of the washers, a hammer worked to break the arm itself loose.
You are also supposed to use new locking washers when you reinstall the arm. NAPA did not have any the right size at the time, so I used Red Locktite instead. Later on I found the right locking nuts at a hardware store, but have never gone back and installed them.
Brucd