Common problem. They are the worst plugs on the car by far. You just can't get your hands in there in to release the tabs, hence all the plier marks on your plugs!
Unfortunately you just have to be brutal with it. It will come off. Have you got any 90 degree picks to prod into the sides to release the tabs?
VW sell new plugs, which is favourable to chopping and soldering. Shouldn't really use solder in the engine bay harnesses. No car manufacturer does because it's not as reliable as a physical crimp connection.