Lots of good questions -- I'll take a stab at it!
Jog vs. run -- that's just semantics. Technically, if both of your feet are off the ground at any point during your stride, then that is running versus walking. Jogging is usually defined as an easier pace than running, but that is based on individual effort/perception rather than a defined speed. (you say tomato, I say tomahto)
A "respectable" 5K time is totally subjective. If you are doing your first 5K, whatever finishing time you end up with not only respectable, it's freakin' awesome! You are out there, setting new goals for yourself and achieving them. Just finishing sets a new personal record (PR) and opens new horizons. Time is irrelevant. Giving your best effort, on the day, and accomplishing such a significant milestone is all that really counts.
And ... if you can complete 3.1 miles on the treadmill, then you are ready to enter a 5K. Why wait?
I can give you some benchmarks. Walkers usually finish in 45-50 minutes (or longer, based on pace). 5K's these days have a lot of walkers, so if you run at all, you won't be last! The winners come in around 15-17 minutes. And everyone else falls in between ... it's such a continuum, any subdivisions would be completely arbitrary.
To build your running base, I'd suggest slowing down your pace to one that is more sustainable for longer distances. Take walk breaks if you need to, there's nothing wrong with that. There's a whole training strategy around run/walk intervals that you may want to check out (http://www.jeffgalloway.com
). There's a lot of good information there about beginning running. As you train consistently, you will naturally get faster. One run a week should be your "long run" which you can gradually extend to the 6 mile /10K distance. The long run should be at a slower pace than your shorter runs.
Enjoy the journey. Races are great fun! Getting out there is all that really matters, finishing time is secondary. You don't have to wait until you can achieve a pre-determined speed, there are ALL sorts out there having fun with 5K's right now.
I hope that helps ...