I'll provide some feedback on your questions and ask your feedback on one of my own. After all having had a freshwater system on my Caldera for a year now I think it's trial and error and time that figures things out.
1) If I'm using the tub (theres usually just 2 of us) several times a week I add the oxidizer (Enhanced spa shock non chlorine) at least once every 7 days and spray off the filter when I do. Every 21 to 30 days I use the spa filter cleaner. My experience has been the shock is specifically for helping the water to rid of the body oils, soaps, finger nail polish etc... break down and vent into the air as a gas or create particles the filter can catch. So with heavy use it helps to use it once or twice a week. The smell you refer to I think is the stinky foot or rank odor that hits the nose when you lift the cover is chloramines the byproduct of chlorine sanitizing after use and sometimes low sanitizer (chlorine levels) like .5ppm to 1ppm. The shock helps to convert the chloramines back to free chlorine or the original state so when the freshwater system is working efficiently you'll get a spike in chlorine ppm from the reaction. My suggestion, and what I find has worked well, is to turn your output down so your Chlorine ppm drops to 2 to 3 naturally before adding any shock. That may be enough to eliminate the odor alone. A few hours after shock I test the water and if chlorine has risen I adjust the salt output down to maintain the 2 to 3. If still low I either add a little dichlor or turn up the output depending on the time of day and our use to hit the right levels. It's always an ongoing process.
2) I'm coming up on 4 months for my current fill and I'm starting to notice more film on the surface water after use and more time to clear up. I highly recommend finding a local pool supply company that provides water testing and use them once a month. You get a specific number on each of your levels and I've found my freshwater sticks tend to be a little on the high side from what my water test printouts show. I keep them all for warranty purposes too for proof my water is being kept balanced and acceptable. I think the freshwater system says "up to 12 months" and I'm more comfortable with every 7 to 8 months personally which is still double what a traditional non salt tub would need. I had phosphate issues during my first fill and was using phosphate remover and clarifier and I realized that adding these things starts to get the foam/bubble effect when using the air valves like what your experiencing. For now on if I have a test come back with high CYA's or phosphates I'm going to drain and refill and just start fresh if the water is over 6 months.
Hope that helps. My question is how much bio film did you see from using the ahh some. I used some flush from the dealer when I drained and couldn't really see any reaction to the water and I've read that ahh some really helps to get the most life out of the salt cartridges.
