A few thoughts / ideas...
It looks like there may still be serrated washers on top of those cones. If so, get those off there first. Use a wire brush to clean off the gunk and verify. I had to use a small screwdriver and a small hammer to unread them the first bit and then they came loose easily.
WD40 is useful for preventing parts from rusting and has some minor lubricating properties, but it is essentially USELESS when it comes to being a penetrating oil. Get some Kroil, PB Blaster, 50/50 mix of acetone and ATF, etc. in there to start actually doing something. WD 40 will never creep far enough in there to do any good.
Once the above is done, take a 3 - 5 lb hammer and hit the front of the spot where you cut the ball stud off from. HARD. Once to try to rotate the arm rearward, then once to rotate the arm forward. It should pop the cones out after a couple whacks. If you use a carpenter's hammer or don't put any effort behind it, you'll be there another week wondering why it hasn't budged.