If you are maintaining a proper active chlorine level in your spa and using sufficient oxidizer to handle your bather load, then you should not normally see any significant Combined Chlorine (CC) except perhaps in the hour or so immediately after a soak. For an accurate CC reading since it is normally so low, you need a FAS-DPD chlorine test such as in the
Taylor K-2006 test kit. So if you are properly maintaining your spa, then you probably don't need to regularly check for CC -- just make sure that FC never gets to zero.
The regular circulation pump is usually sufficient to ensure thorough mixing. Putting on the jets will aerate the water and tend to make the pH rise faster.
The Taylor watergram is accurate, though you can also use
The Pool Calculator to calculate the saturation index and to calculate dosages (after changing for the spa water volume, of course). Note that 1 ounce is 2 tablespoons or 6 teaspoons.
For an acrylic spa, you do not need to have the water saturated with calcium carbonate since there are no plaster surfaces or grout surfaces between tile to protect. To reduce foaming, the Calcium Hardness (CH) can be at 120-150 ppm. It sounds like you have high CH fill water since it's on the high side (unless you added to much CH increaser).
A rough rule-of-thumb for how much oxidizer is needed to handle bather waste in a hot (104ºF) spa with no ozonator is that every person-hour of soaking needs about 3-1/2 teaspoons of Dichlor or 5 fluid ounces of 6% bleach or 7 teaspoons of non-chlorine shock (43% MPS). If you have an ozonator and use the spa every day or two, then these amounts may be cut roughly in half. However, the real test is to check the FC level before a soak and ensure there is always some measurable amount (at least 1-2 ppm) and then add enough chlorine after the soak so that you measure FC before your next soak.
If you are using Dichlor-only, then over time the Cyanuric Acid (CYA) level will build up since for every 10 ppm FC added by Dichor, it also increases CYA by 9 ppm. This will make the chlorine less effective over time so you will need to either shock the water with higher chlorine levels after a month or so or you'll need to use MPS to supplement oxidation. If you instead use the Dichlor-then-bleach method, then you may never need to shock nor use MPS, but the use of hypochorite sources of chlorine (such as bleach) requires the Total Alkalinity (TA) to be much lower (around 50 ppm) and the use of 50 ppm Borates (such as from Proteam Gentle Spa or boric acid purchased directly) is recommended.
