I use a small pipe wrench (6") it works better than vise grips. The more force you apply, the tighter it gets.
But in this case, if it is rusted that bad, I would just go for the new wheel cylinder. There is one little bolt directly under the bleeder screw that holds it to the backing plate. It will probably break, but who cares, you are going to ditch it anyway.
I would also do a brake fluid change. Brake fluid tends to hold moisture and rust from the inside out. I use a Mity-Vac to suck it all out from the farthest place from the master cylinder first, then to the next place, and so on till it runs clear all over. It will take a quart or so to do the flush, but it is money well spent IMO.
BTW, little trick for the brake lines - try tighening them a little bit before loosening them - it helps to break them free. Use GOOD line wrenches. Cheap ones (and Craftsman) tend to spread open under any force. Spend the bucks and get a Snap On and you won't have issues with them stripping the fittings. You only need one...