What is your running background? How many years have you been training? What are some of your other race times?
Generally I would agree with what the other posters are saying, but honestly, you're 50. For must of us as we age, that changes things a LOT. 9 hours a week of running is great if you've done something like that in the past. If not, it might take you a really long time to get there safely. And it might not even be possible.
Your 8k time suggests the sub 2 is possible. It will likely require more time and mileage, though. But I think you could maybe do it in 8 weeks. Especially if you have good conditions on race day.
I would focus on the long run and a mid-week tempo type workout. For long runs, alternate going longer and easier. So like you've been doing, but see if you can hit 2.5 hours on those days. You might need to work up to that. For the opposite weeks do something with more pace to it. I like progression runs. Start easy around 11 minute pace, work your way down to the 10's after a few miles, then into the 9's and see how long you can cruise there. 10-12 miles of that should feel doable. After a couple of these, see if you can hit high 8 minute pace in the final mile or so.
Mid-week get some classic tempo work in. Or just a hair faster. It sounds like you do a lot of straight tempos. Up to 40 minutes. That is on the long side. Split the tempo up in other ways. You can do 5 x 1 mile at tempo pace but jog an easy 2 minutes in between. 10-12 x 3 minutes at tempo or slightly faster and jog easy for 1 minute. Stuff like that. People get caught up in the details of these workouts, but I think the important thing is putting in the time at those paces, and doing slightly different workouts just to keep you a little more fresh.
All other days run really easy. Maybe get out in the evenings (if you run in the mornings) for a brisk walk. It is amazing how extra walking can improve recovery. Very easy on the body. Some easy biking might help, too.
If you can find a 10k race about a month before the half that could be really nice, too. It's good to get that experience of going hard. It's a great workout. And it will give you another data point to see how you're progressing.