Milly, I’m SOOOO sorry I didn’t see this sooner.
I’ve been away for a couple of days with a few gal pals. We needed to cheer ourselves up with an oestrogen fix.
So, let's see ...
1) How long before you notice any real improvement ?
This depends on your base level of fitness, and your past running experience. As you may know, muscles have a sort of "memory". If they have done something in the past, it's easier to make them do something again, even if they haven't done it for a long time. Like ... riding a bike, or roller skating.
If you've been running in the past, your muscles will get accustomed to your running regime more quickly. It will "all come back to them". Likewise, if you have had a good level of fitness for a lot of your life, then it will come back more easily.
It might take a few weeks, or even a bit longer, but ... it WILL come. It might even creep up on you unexpectedly. You'll suddenly find you are running a bit further, a bit more easily, and you hadn't noticed.
Have you tried sticking with a fixed distance, and only increasing it when you find it easy, and when you are doing that distance a bit more quickly?
2) When you do the half marathon, can you stop running and walk the rest of it?
Yes, absolutely.
(continued)