These are all resolved.
1. This was user error. Bit confusing, but "All Fills over All Strokes" and "All Strokes over All Fills" are accessible via Text Layer > More Options > Fill & Stroke. This property can read/write via scripting.
#2 and #3
These both work for read/write back to AE 2021! Documentation at docsforadobe.dev was previously inaccurrate and has been updated.