How to clean scale without affecting chemistry?

It looks to me like you have surface water draining into your pool from under the deck. If that has been fixed, I would clean off the Calcium deposits with acid and you should be good to go.

It may stop on it's own but I doubt it.

You could simply clean the tile with acid from time to time but the permanent solution is to redirect that water so it stays out of the pool.

Efflorescence occurs when the water seeps through the finished surfaces, Your appears to be cioming from the top of the decking, draining to daylight and then down onto your finished surfaces.

Muriatic.

Start with a ratio of 4 water 1 muriatic. If it's really stubborn 1:1, but try it weaker first.

You will see it foam or bubble up when you apply. Rinse thoroughly and immediately once it is clean. OK to let muriatic drain right into the pool.