The black dot should totally disappear. It is definitely the hardest test to read.

I'm not sure if you are also posting over on TFP, too, or not. TFP was created long after Pool Forum and was basically a spin-off of PF built on the ideas they learned here. (In fact, many of there original members are former members of PF.) However, if you are posting for help on both forums, it is best to choose one or the other. Though mostly similar, we don't totally give the same advice and it makes it hard for everybody if you are trying to use bits of both. Plus it makes it hard for us (and them) to help since we have no idea what advice is being given on the other forum.

Personally, I would not take my vinyl pool up to 39 or 54 unless lower shock levels wouldn't kill whatever type of algae I might have in my pool. Really high levels can bleach out liners. So, I would go with 18-25 and brush and see if that will take care of your issue.