Yes, part time federal employees pay higher premiums when they work over 15, but under 40 hours per week. Interestingly enough, if you only work 15 hours per work (been there myself) you pay the same premium as a full timer, but over 15 until full time you pay a prorated amount.

As for who the other insurance questions, I don't know. That stuff is pretty sticky....just try to hang on to the federal plan.