The impossibility of Star Wars Star Killer

I finally get a chance to see Star Wars: The Force Awakens and I find I really have to turn off my "disbelief / scientifically impossible " button. Let me address the "Star Killer base". ( yes I know it is just a movie, but common!)
So this big weapon that makes the death stars look like ping pong balls in comparison gets its power by siphoning hot plasma from a star. Some big problems here.
First: Siphoning the plasma itself would require tremendous amounts of energy. You would need a device to pull the plasma from the star and contain it. The device would need so much power you might as well just use that power to power the weapon.
Second: If the weapon was just beams of plasma it could not travel at a speed fast enough to make it a very effective weapon; which would have to be the speed of light. I don't have to break out the old e=mc^2 thing here then manipulate it around to show how impossible this is do I? Let me sum it up like this very simple rudimentary: when you accelerate a mass close to the speed of light the said mass will gain energy hence more mass which requires more energy to keep accelerating so if you work it out you would find to hit the speed of light you would need infinite energy and of course the object would have infinite mass. Not happening.
Third: you would probably blow up the star powering the weapon before you could destroy a targeted planet. "How can that be Chuck? You are taking energy away from the star not putting energy in." Well here it is. You see stars like our sun are in a state of equilibrium where the radiation pressures that push outward are kept in check by the gravity of the star. Now if you take a large amount of plasma which has mass from the star the reduction in mass will mean a reduction in the gravity of that star. And even though you have taken plasma, which is energetic, the radiation pressures created by the star's internal fusion would be greater than the gravitational field and the star would expand and because it is not a natural phenomena it would probably nova.
Fourth: that much energy in the plasma would fry and melt everything on the planet so it would look worse to Darth Vader's mask!