Questions about clearing signup bonuses

[Quasimodo63]

First off I apologize for the newbiness of the questions. I have done extensive searching and have answered many of my rookie questions already. I would like to engage in sports betting clearing signup and reload bonuses and build a bank roll risk free. I have about $10,000 in poker money I can use for this. Here are my questions. Thanks in advance for all of your help out there.

1. When a site offers a bonus, it mentions how often the deposit has to be rolled over. What happens if you bet all of your deposit and lose it before rolling it over enough times?
2. How do most of you make your wagers? My impression is that you use two sites and bet them against each other. optimally, you find two sites that have different spreads. If one site has the Steelers -3 and another has them -5, you bet both teams and hope the Steelers win by 4. When doing this, does the profit come from hitting the middle on occassion, and having the bonus more than cover the vig??

3. How much could I make starting with a modest $10,000 bank roll, betting at a mediocre level of skill (I'm new, but do my research)

Thanks for any suggestions, tips, etc.