For sure – I can totally understand that and I’m glad to hear you’re able to leverage your previous training experience to your advantage.
Here is a sneak peek of what we’re working on for situations like this straight from our CEO, Nate Pearson, if you’re interested. Basically, we’re working on a big update that will help get athletes “locked in” to the right workouts even faster than AT is currently capable of doing.
Since your Threshold workout for tomorrow seems a little low based on how you’ve described your plan, I used our RPE Prediction tool (which is incorporated into how TrainNow functions after recent updates) to find a replacement – I went ahead and replaced your original workout with “Warlow,” a Threshold 4.7. It may be “hard,” but it should still be doable. 
Once you complete that workout, your PLs will update and keep you on track.