(1) The text in one of the quant questions was cut off on the computer screen. I raised my hand and told the proctor about it, but he said that he couldn't do anything. Is it possible (or probable) to successfully raise this to GMAT's attention and get the question thrown-out?
Yes, you should contact GMAC and file a formal complaint immediately. For future (and for others reading this), you can file a complaint at the test center itself and you should do so - get the system rolling right away. (After the test is over, of course.)
You should mention in your complaint that you brought this to the proctor's attention and that the proctor both said he couldn't help you and didn't suggest that you file a complaint - basically, he didn't help at all.
Is there any way to get more than one scratch pad prior to starting the test
No, we're only permitted to have one pad at a time. Raise your hand when you still have some room left - at a point where you can let the pad go when they come in (eg, you don't have 5 lines of calculations and you need one more line to finish when they want to take the book).
Also, practice using your scratch pad more efficiently. You have 9 legal-sized surfaces and 37 quant questions, which means you can use a quarter of a page for each question. That's a lot of space, if you use it efficiently. Then, you don't have to change during the quant section - you can change at the break. Ditto for verbal - you have just under a quarter of a page per question, on average.
One, is it feasible to improve my score to a 700?
Sure - there are plenty of people who start out in the mid-500s "cold" and then get up to the high 600s or 700 after they study. Not everybody will, of course - you have to do the work and you have to do the work
well in order to get to a 700. You'll need to read up a bit on how best to study (there are lots of posts you can examine here and there are also a lot of good resources at
www.beatthegmat.com) and choose the tactics / techniques that you think will be best for you (your strengths and weaknesses, your learning style, etc).
Most people looking to go from 550 to 700 take somewhere between 2 and 4 months to study - depending, obviously, on how much work you do, how frequently you study, and the kind of progress you make over time.
You'll also obviously have to factor in any deadlines if you're planning to apply for this year - but I'm guessing not because we're already pretty late in the application season for US full-time programs.
Good luck - let us know how it goes!