The "simple" answer is just run a lot. 45 miles a week is really low for a collegiate miler, and that's the most you've ever done. You probably don't have a whole lot of talent, but you're also nowhere near your potential. You can get A LOT better just by running more. I think a good winter training goal would be to hit 70 mile weeks by the end of January. That's about 13-14 weeks, so if you build up something like this:
30-35-40-40-45-50-50-55-55-60-60-65-70
You can get there without (probably) killing yourself.
I wouldn't worry about a rigid schedule. Once a week do a long run of about 20% of your weekly mileage. Doubles are good, an easy 4 miles in the morning will help you without killing your afternoon session. Once a week do something harder, a tempo, fartlek, whatever. Those can be done on the roads even when the weather is pretty nasty. Maybe hop in a road race here or there instead of the workout. Try to measure out a place to do 100m strides once or twice a week at mile pace.