how many miles per week before you could "comfortably run a half

I have done three halfs & one full marathon and have always used a plan. The one I like the most is the Hal Higdon half marathon plan( check it out on the web). Its a gradual build up.  Bart Yasso from Runner's world also offers some great plans & tips.

What kind of runs are you doing during the week beside the long run?

I think I was running about 20 miles/week when I did my first HM. I did a couple 10 milers and a 13 miler in training, but most runs were in the 4-6 mile range. I didn't use a plan. I just ran. After the HM I decided to do a full and signed up with a group training program. The training was pretty much like many beginner programs and left me substantially undertrained. The first marathon was dismal as a result.

It looks like you run about 15 miles/week. That would make your long run about 50% of your total volume. That's too high and may be the reason you struggle. You can either add more distance to your other runs or add more runs to bring the percentage down to no more than 30%, preferably 25%.

I used the Hal Higdon plans, and I'd be surprised if they reached 20 mpw.... I did my first half in 2:17 with this plan: http://www.halhigdon.com/halfmarathon/novice.htm

Now, I don't know that I would say I ever "comfortably" ran a half. It always hurts a little.  But I felt prepared, for the most part.  Not great or fast, but okay.  You have to be able to do the longer runs, though.   I am concerned you're struggling with 7-8. 

     right now your can run 7-8 miles . you might  not  think it  but  you are almost there.  first how long does it take for you to run 7 miles. . let's say 1  hour and 10  min. your looking for a half at the end of nov. so that gives you around  11 weeks . keep running you 5-6 miles 3 day a week , on the 4th day which would be   a 7 mile  run. now look at your time , ex 1 hour and 10 min. try adding  10-12  min a week durning  your long run . . try working up to 2 hours . now it does not have be be 2 hours on the mark , but around  that  time. the half 13 miles , so with 10 min miles your time would be around 2:10. your  just looking  to finish . so don't worry about comming in  under 2 hours. also do you train with  heart rate monitor , if not try it. i have run 6 marathons , and 1 ironmman , and 100's of half marathons. after years of training and looking at the mile mark, now i just go by time.
     also  when i run  for over two hours . i like to take a easy 3-5min  break . what i mean if i  an running at  a heart rate of 140 beats . i cut back to 120, two things , one if gives  your body a break, and 2nd it also a mental break. i have used this during the past marathons. it just like jeff's running and taking a one  min walking break. by the way that's a great program for first time marathons. good kuck , i don't know if this helps . but it's works for me..