First off, I think, using an SWCG, your levels are probably incorrect. SWCG usually call for a CYA of 60-90 ppm, generally 80ppm. At any level FC should be 5% or more of the CYA. But I've not heard of an SWCG system that recommended a CYA level that low. Second, you have both what I think is an algae problem and a low grade CC problem. The cure for both is to shock your pool to at least 15ppm and maybe 20.

We don't say don't shock your pool. We say don't shock your pool if it's not necessary, but definitely do when it is. And I think it is now.

You did not mention your pH. Higher pH makes the water less irritating but makes chlorine less effective. If your pH is running at 7.8 or higher, I think you need to lower it. If it "trends" high, then you should lower your TA as well. I KNOW higher levels are recommended but that's not always right. This past summer I ran TA at 60 and almost NEVER had to adjust pH, which stayed between 7.5 and 7.6.

CH levels are recommended for hard pools between 200 and 400ppm. But if you're getting grout loss at 250, you may need it higher. Not sure what you can fill the spaces with underwater except underwater epoxy, but as for looking nice....Someone else will have to advise you.

Carl