Your AGI takes into account everything after all income (base salary, housing, travel, education, etc.) is calculated and adjusted for all legal deductions (housing offset, per diems, other taxes paid, mortgage interest, etc.).
After you apply the exclusion, you pay tax at the rate in effect if you hadn't applied the exclusion. It's a change from the way things worked a few years ago, but it's better than nothing.
I agree with TP's suggestion about joining the local US Chamber of Commerce. They do good work and are generally well respected on the Hill.
And, don't get hung up on the 330 days issue. If you are a resident on a resident visa, the bona-fide resident status will cover you.