1. The USAF. But there is a risk nowdays of becoming a fixed-wing UAV pilot.

2. All branches are more or less equal (military benefits are standardized), but Navy and USMC place more emphasis on being a military leader/manager...ie you will have a real job too. In the USAF you have a better chance at just being a pilot, at least as a junior officer.

3. If you apply to all services, your odds are reasonable with your GPA (especially if you had a technical major...they know the difference between EE and Poly Sci)). This assumes that you are reasonable military material...fit, athletic, people skills, can pass the medical exams, no background problems. The look at the whole person and the more well-rounded you are, the better.

4. Varies, but on average poor. Sometimes extremely poor. There will be unaccompanied overseas deployments, sometimes 6-12+ moths. In the Navy/USMC you tend to work long hours when you are home, I think the USAF and army are a little more reasonable when you are not deployed but it depends on the unit you are assigned to.

Be aware that the Coast Guard, Army, USMC, and Navy have a high chance of assigning you to helicopters. If you aspire to be a career civilian pilot that can be a problem because helo experience does help much with airlines and other civilian jobs. There are ways you can acquire enough fixed wing time even if you become a helo pilot, but it's not guaranteed that you will get such an assignment.

Most of us who have been around the block would VERY strongly recommend the USAF reserve or Air National Guard. You join a particular unit, so you know up front what type of airplane you will be flying...you can simply not apply to rotory-wing units if that's an issue for you. Also you can work on your civilian career in parallel with your military career.