Haha maybe someone else can weigh in on the hairAs you can see from Avatar - I am not one to consult with on hair ------
Though I would suppose that pH and CC has more effect than FC.
Sand should be fine unless compromised. If your deep clean did not find it clumped up, then it should be fine.
Start planning now for vacation. Get your CYA lower as you can as you will need to use trichlor. Can a neighbor add liquid chlorine every once in awhile?
I will have my mother in law available to add chlorine, but I'm not sure we would have her do any testing. Hopefully by then I'll have a sense of how much maintenance chlorine is needed. We will leave the solar cover on while gone. Hopefully with a bit more backwashing between now and then we will see lower CYA.