Congrats on the new hot tub!!!
To answer you questions:
- I recommend to my customers to use "Clean" mode when they are adding chemicals. It's nice because the pump only runs for 10 minutes and shuts off instead of running for a much longer time if you just hit the jet button.
- If you have a hot tub party, not a bad idea to use the Enhanced Shock then. Otherwise, under normal usage, I think once a week is fine.
- 3 weeks could be normal for that SmartChlor cartridge. What setting do you have it set on and how many hours daily is your hot tub filtering? Also, how is your pH? Low pH will deplete the cartridge A LOT faster than it would otherwise.
- Water that is discolored, cloudy, or has a musty smell are all signs of low chlorine
- Typical water level would be 1/2 way between the uppermost jets and the headrests
- I would just use a non-abrasive sponge/scrubber to wipe anything off. When the hot tub is empty, I tell my customers either vinegar/water mixture otherwise I sell Off The Wall by BioGuard.
- Can't help on the chemicals. I always suggest buy from your dealer if possible. They are usually the ones answering your questions and the one that will be performing any service needs. As a dealer, one of my biggest pet peeves is when customers use me for water testing and pick my brain only to buy stuff elsewhere. I treat all my customers the same but I will go the "extra" mile for those that continue to support my business.