How should I spend time in Zone 2? Staying between 130-140bpm is really hard to do while running and basically I just need to do incline walking for now.
You answered your own question. And it will likely never change on inclines. Very few humans can run uphill at an aerobic level of effort. It’s normal to have to walk or hike.
1. When on a treadmill, there is a tradeoff between incline and speed. How do people decide or vary their incline? The treadmill I have access to can go to 30 degrees.
If steeper, go slower.
2. If I do inclined walking, when should I transition to running? I find my heart rate is about 7bpm faster while running vs a fast walk.
Let your heart rate be the deciding factor. The priority right now is to fix your ADS. Regardless of the activity, stay below 140. Gradually, the speed will increase. In future tests, your aerobic threshold heart rate will be higher (with proper training and patience).
3. What do you think of the proposed schedule?
This may be too high a volume to start with. I would start with 30-45′ 5-6x per week and see how that goes. Shorter, more frequent sessions will have a better training effect than longer, less frequent sessions.
4. How long should I do this (time or markers) before reassessing or changing my approach? I’m planning on 12 weeks which puts me at the end of July.
In six weeks, try a drift test to see if AeT HR has changed. (Search the site for hos to do one.)