You need the socket. An auto parts store may have a b/j socket kit for loan or rent or purchase. Avoid heating the control arm as this may change or weaken the temper of the metal. Follow the procedures and torques listed in the service manual.
An impact tool may not be effective with the arm mounted in rubber bushings. It 'gives' too much and the rubber absorbs the impacts.
A 3/4" breaker bar should crack it loose and the impact may unscrew it from there. If the vehicle is supported on jackstands, may sure that it stays on them.
A foaming graphite solvent/penetrant may help with the threads.
Yeah, that's what I had to do for the Cordoba... A massive breaker bar and a lot of pulling. I think that the second car I did I installed 'em with the breaker bar too, which was actually faster than using air...