I think Daniels writes for pretty experienced runners, so to jump right into a plan like that having not had structured training it could be pretty difficult.
I do a little bit of Daniels mixed with some other workouts and an easier "easy" pace. I've run 2:20:11 and it has my "easy" at 6:09-6:33. Sometimes I'll run in that range if I'm pretty fresh/it's a good day, but the majority of my easy is a good 20-40seconds slower than that range and I've been fine. I feel 6:10 most days is way too fast, I think those are easy ranges for people who do nothing but run (I'm a teacher and run many runs at 5am, definitely not running 6 flat then)
The 12mi T in a long run is a very standard workout for Sub-Elite/Elite; there are videos/posts of the NAZ/BTC guys doing that stuff often. I'll go up to 12mi but not at "Tempo" which according to Daniels my "threshold" is like 5:10 which if I ran 12 at that routinely I would be exhausted. I use Daniels workouts but substitute my paces with Canova and I think it's a good blend. Link for Canova's workouts/Training Pace conversion: https://runningscience.co.za/elite-athletes-training-log/renato-canova/
For reference my MP is 5:20, and when I do a 12-15mi LR tempo I usually will average btwn 5:35 and 5:40. I hear local marathoners (usually 3hr+ guys) running sub marathon pace for their 10-12 tempo all the time and I always ask why?
4x2 + 1x2 is a bit intense after, I'm not sure I'd have both in the same week, maybe I'd wait until the next week. Never think you have to 100% stick to a plan. Have a plan/goal and alter it as needed!