Good work Fgin things are moving along nicely. Just about the salt levels- the recommended salt levels for SWG's varies between makes and models. My Davey SWG recommends between 4500 and 6000. I've looked your model SWG up and yours is simply around 4000, so that should be more or less what your ultimately striving for. If there is no low salt indicator showing, then you can assume that the SWG has enough salt to function without damaging the cell. But yes if you want to calculate your CSI- you need to key in a number. To tell you the truth I have not gotten around to purchasing a salt test in the 2 years I've had my pool, and so have monitored my SWG chlorinator closely so that when the salt level gets low and the warning indicator comes on I simply add a couple of bags of salt straight away- its not the ideal way to do it and soon enough I will get the Taylor salt test. I have used Clarke Rubbers pool testing and I have found their salt number pretty close to what I roughly thought, keeping in mind the optimal range for my SWG. But yes I would strongly suggest getting the Taylors salt test, maybe when you place your next order for some refills for your K2006C.
Your FC indicates that you are in the ballpark for maintaining your chlorine levels at the moment- keeping in mind that hotter temperatures (more sunlight) and bather load will have an impact on FC demand, so you really need to keep the FC testing regime daily in the lead up to summer ( or at least until you can start seeing some patterns about your FC loss relative to these 2 things). Keeping in mind you will probably be adding more stabiliser to bring your CYA level up to the recommended levels for a SWG and reducing loss to sunlight. The most important thing is not letting your FC drop below the minimum for your FC/CYA level.
I would also test and record your PH level level daily to see what's happening, with a TA still high you would expect that this will keep going up but whilst you keep adding acid it will also be bringing down your TA to a level where PH will begin to stabilise.