A few things:
1) Your PR's all seem to line up pretty well across the board. I think you can probably run a faster 400 than you have on your list but it makes sense because you probably don't actually run all out 400's on a regular basis.
2) "Should I run more miles?" Is a loaded question without knowing what type of training you're currently doing. If you're just going on 3-5 mile runs 5 days a week, then no, you don't need more miles. You need speed training. If you're doing 2-3 workouts a week and running 2-3 easy days, then maybe you need more specific focus.
3) Most 2min HS 800m runners run somewhere between 15-25 miles per week. These are 400-800 runner estimates, not guys that specialize in the mile and 3200, but also run the 4x800. So you don't NEED to increase your mileage.
There are tons of different energy system charts but the one stuck in my head for the 800 is:
Aerobic (endurance): 40%
Glycolytic (extended sprint): 55%
Alactic (5 sec burst): 5%
This suggests that endurance training is less important for the 800.
4) Getting to 2:05 from where you currently are is very possible this year if you focus your training for the 800 (which is very different from 5k training). Breaking 2 minutes from where you are will likely take a long time.
5) I saw an earlier post of sample workouts to do and I would politely disagree. If you're running 20 miles per week now, getting up to 50mpw while throwing in tempo runs and 10 mile progression runs is the opposite of training for the 800. Plus, if done correctly, increasing your mile from 20mpw to 50mpw will likely take 3-4 months, which is unnecessary if you’re training for the 800.
If you want to get under 2:05 this season (Spring), and are fine ignoring training for the longer races while doing it, a really simple plan would be something like:
(I am pasting this from an email I sent to one of my former HS athletes that decided to walk on to her college track team in the Spring a couple years ago. It's not perfect for you (or her), but it's a starting point, and I made some slight changes as a read through it. No, I did not create an entire workout plan during my lunch break lol)
2 weeks running reorientation period:
Run 4-6 easy 20 to 30 min runs a week. Do weights/general strength 2-3 days. And do 6x100m strides (around 15 sec for you) on the days you don't lift.
4 weeks of specific prep: Example:
Monday: 1 mile warmup, dynamics/drills, 4x400 @ mile pace, mile cool down, lift weights
Tuesday: dynamics and drills, 30 minute easy run, and strides
Wednesday: 1 mile warmup, dynamics/drills, 8x100m at 200/400 pace, 1 mile cool down, lift
Thursday: dynamics, 20-30 minutes easy, strides
Friday: dynamics, 30 minutes easy, strides, and weights
Saturday: 45 minute long run.
Sunday: Off
Week total = 23 to 25 miles (including warmup and cool down miles)
2-4 weeks of pre competition training: (still not racing yet)
Monday: 1 mile wu, dynamics 6x400 @ mile goal pace (or switch it up with 4x600 or 3x800), cool down, lift
Tuesday: Dynamics, 30 min easy, strides
Wednesday: 1 mile warm up, dynamics, 8x100 @ 200/440 pace or 3x (50m, 100m, 150m) all at 200/400, cool down, lift
Thursday: 20-30 minutes easy, strides
Friday: 1 mile up, dynamics, 8x200 @ 800m pace, mile cool down, lift weights
Saturday: 35-45 min run
Competition period: Pretty much the same as above, but only lift twice and do 2 workouts
Monday: 1 mile WU, dynamics, 8x300 @ mile goal (of do a speed endurance ladder 200, 300, 400, 600, 400,300,200), cool down, lift
Tuesday: Dynamics 30 min easy run, strides
Wednesday: 1 mile up, dynamics, 6x50m @100%, cool down, weights
Thursday: 30 min easy + strides
Friday: Pre race routine (easy run + strides if you don't have one)
Saturday: Time trial
The above is something I thought an 18yo girl (that ran 4 years HS track and cross) would actually do on her own unsupervised. Again, it's not perfect, but as a 27yo novice runner, that probably doesn't have a coach, and probably works full time, this is something you can do in your spare time. Also, do some research and change the workouts around. This is just an example/guide. Have some fun with it.
The key is alternating: Threshold, recovery, pure speed, recovery run, speed endurance, recovery run, off. You can switch the order. You can piggyback workouts if you have a busy week. You can skip threshold one week and do more speed endurance. It's a balance. Find out what works for you. Lift on workout days, not recovery days, so you allow your legs to actually recover on recovery days. That’s really it.
Good luck with your training. Hope you crush it.