The first two are easy answers to get from recruiters, or at least once you have a job offer. And you should go to more than one interview. If you get two job offers and one place says you can start next week while the other place says October, go with the job that starts next week. Heck, if you love the place that starts in October just park any bonus money you get, then in October turn in your two-week notice and go with the other airline if you want.
Usually, there is a correlation between how quickly you can start class and get through IOE and how much you will fly/sit reserve. It's usually an indication that the company is very short staffed.
Reserve. People talk about reserve like it's the end of the world. Now if you are commuting, yeah. It sucks. But if you live in base and have a good contract reserve can be nice.
Good luck.