The base (longer) runs are at 80-100% of Aet (Zone 2?), and the recovery (shorter) at 70-80% (Zone 1).
In general, we recommend that Zone 2 be set at 90-100% of AeT, and Zone 1, 90% and less.
Bearing in mind the lack of ADS, should I switch the longer workouts to zone 1 and the shorter to Zone 2?
It depends entirely on fatigue. At some point, you’ll have the realization that you can’t sustain a lot of volume in Zone 2. That may not happen right away, because it depends on speed. As your aerobic capacity increases, your paces at each intensity will increase. Eventually, Zone 2 training will feel more like Zone 3 in effort.
In my own training, my HR thresholds were very close for almost ten years. It was a long time, probably because I was very active with a lot of volume, but without much structure. Once I was on a progressive, structured program, it took three years before I had to back off on Zone 2. I just had the realization one day, “I can’t do this anymore.” At that point, almost all of my training shifted to Zone 1 or lower. (I now use a “Zone 0”.) It’s not uncommon.
The roads would be to increase my cadence and actual running because I’m considerably slower on trail. Would I be sacrificing base by being quicker on the road?
I don’t think that there’s a disadvantage, especially with your marathon not having a lot of gain.