I think a realistic goal for drastically increasing your mileage from 45mpw to 80-100mpw would be:
1. A stress fracture
2. Achilles problems
3. Another stress fracture.
Just doing more is not going to make you any better. The part of the training that makes you better is the adaptation process your body goes through in your recovery. If you don't have enough recovery, you will only break your body down. For someone with so little running experience, I doubt you can handle doing 80-100mpw consistently. You might be able to hit one 100mpw and then a couple 30-40's. If you actually run 1:15-1:17 for your first half on 45mpw, you can try to go to 50 (or at the max 60mpw) first and see how you do on that. I bet that you would even improve if you keep on doing 45mpw, since you have so little training background.
If you really want to hit an arbitrary 'magic' number, you should do that. But that better be your main goal because 9 out of 10 times such a drastic increase in mileage is not going to have the desired effect.