would it be possible to accept "I know his every action"? it's just as natural and actually is a more word-for-word translation
Yes, I think you are right, I would think you would say "tất cả hành động' for "all his actions".
If I can hear it, it is possible for anyone. My guess is the "ộ" part the accent that may be tripping you up.
don’t quote me on this, but i think mỗi has more of a sense of ‘each’, while mọi is more like ‘all’ or ‘every’
I have been thinking about it too, but unfortunately for me I don't really distinguish between "each" and "every" (English is not my native language).