OK, here are the results from my testing.
Mar07 Buildmlv_lite1776x1000, 14-bit lossless, 16:9
Preview: Realtime
40 min. -
OK--------------------------------
mlv_rec1792x716, 10bpp, 2.50:1
Global Draw: Allow
40 min. -
OK--------------------------------
mlv_lite + sd_uhs1832x1024, 14-bit lossless, 16:9
Preview: Realtime
40 min. -
OK--------------------------------
mlv_rec + sd_uhs1824x1026, 10bpp, 16:9
Global Draw: Allow
40 min. -
OK--------------------------------
mlv_rec + mlv_snd1792x716, 10bpp, 2.50:1
Global Draw: Allow
Err70, after a few seconds--------------------------------
Mar14 Buildmlv_lite1776x1000, 14-bit lossless, 16:9
Preview: Realtime
40 min. -
OK--------------------------------
mlv_rec1792x716, 10bpp, 2.50:1
Global Draw: Allow
40 min. -
OK--------------------------------
mlv_rec + mlv_snd1792x716, 10bpp, 2.50:1
Global Draw: Allow
Err70, after a few seconds--------------------------------
In all the tests I used ISO100, 24 FPS. A run the first test for 40 minutes and decided to run all other tests for as long, not just for consistency, but also to test the camera's stability. All tests were done back to back, using two batteries - one being used, while the other was being charged. The camera was pretty warm throughout, but didn't pass 58*C. According to Canon, Err70 occurs with prolonged use and supposed heat build-up, so I had to test for that. I don't know anything that heats up cameras and drains batteries quite like shooting RAW video, so I guess my 70D passed the test. Anyway, the result is that the
mlv_snd module always produces Err70, when activated, unfortunately.
@ArcziPL
1. I tried setting the audio to manual and turning on and off the wind filter and attenuator, but it didn't help
2. There's absolutely no problem with the camera taking pics and shooting h.264 with or without ML loaded
3. I think my test results answer that one

4. Tried that, too - doesn't work