That is one crowded sump.
To answer you question about salt creep. It's just dried salt outside of the tank. If your return line is pulling air(venturi), there will likely be some salt creep at the connection. Not always though.
I wonder. Could a pump produce micro bubbles? Maybe my main return pump is causing them. I look near the return pump with a flash light and I do not see the bubbles. If that is the case how could you even begin to diagnose it? I do notice when I unplug the pump and plug it back in the pump spews out a ton of bubbles initially.
Definitely possible, although your pump is being damaged if that's the case. This would be due to
cavitation around the impeller. I don't think this is the case though, as it would have gotten worse when you slowed the flow even more.
As others have stated, without a set of three baffles, you'll likely keep having bubbles in the display. I think your sump needs a remodel. Looking at the pictures, it looks like you have two reaction chambers. If you can, try to mounts these outside the sump(shouldn't be an issue). This will free up a lot of space to install three baffles, one inch apart. Scrap the maxijet for circulation too, shouldn't need it.
Put all equipment and reactor outputs in the big chamber, The small chamber will have your return pump and your ATO switch.