get some wd40 on the adjusters and get them lower on the strut, you will de-compress the spring and there will be no need for the compressor.
And yes, you can get new springs from gaz or gaz suppliers. For the top mount you may heve to use some kind of extractors. I remember it was a pain for me as well to remove them from my old suspension when I fitted the coilies
I'm having some other issues with my gaz coilies, and while you have the strut off the car, can you measure the distance from the bottom adjuster to the lower end of the shock? I'm curious to see how low your car was with the ride height set up like that.
Hope that I've been of some help with your problem