Sorry for the late reply. For the first question, both itch and humble bundle sales earn me the most money. For the second question, in theory mod support should be similar in steam and non-steam versions, but unfortunately I still haven’t solved all the technical issues with that, so non-steam versions have a bit of lag (you might see mod versions that are a few weeks older). But in the long run, this should be solved and mods should update with up to one week delay.
Note that buying from both itch or humble, you can still redeem a steam key and play the game on steam. The steam version is DRM-free too, it’s exactly the same version of the game, it’s just able to connect to the steam workshop if run through steam.
Hope this helps.