since you seem to like intervals, i have a suggestion to make them more of an aerobic workout (keep the rest short).
For example; on those 20x200 (i would break mine into mini set of 4 or 5 and start out at a medium pace on the first set with a short as rest as i could take.
5 x 200 in :38 (only 20 seconds rest) these will feel real easy
5 x 200 in :36 (up the rest to 25-30) these will feel good
5 x 200 in :34 (30-40 rest) these will make you breath harder
5 x 200 in :32 (45 rest) these will push you
i might take about 2 min between each set or whatever i needed to get reset. on caution: when doing workouts like this where you take super short rest and increase it...i have noticed that the first rep of each next set it is easy to go way too fast (because after that big rest of 2 min between sets - you will be way more rested than after those in between intervals where you are only getting 20-30 seconds rest). so ease into the first one - even be a little on the slow side...because if you blast out a 30, you are going to be struggling the rest of the set and kinds of defeating the point of making the workout more aerobic in nature.
I might also limit my intervals to just one session per day (vs the double intervals) Might replace that second run with just a good old fashion easy 8 miler (and maybe even let this be your one slow day where you intentionally go super easy) there is value in going slow.