I have just found a similar problem in this forum discussion.
The solution given by James @acf-support is the same as the one given by @keithlock.
Interestingly, re my point #5 above is silverdarling’s remark:
Good thing is that wysiwyg.php looks like its primed to go for adding wysiwyg height via admin interface.
This is similar to gallery_height being “primed” for setting, but again WHY is this not working?
