Have you tried taking out those screws and seeing how it's connected on the inside? That would be my first step after the yanking-on-it method.
maybe try twisting? It could be a 1/4 turn lock. Then I would try removing/loosening the screw in the recess above the antenna
pretty sure the screw doesn't do anything. That is actually to take the radio apart.
That cable was frustrating to pull out. Took quite a bit of force to remove it.
Did you remove the cable just by plugging it out directly? If so, I'll just use a pair of pliers and a lot of force.