Starting slam: have questions

[nutria]

So my pool turned green ...
We got a new house with a pool but took a while to move in and could only do semi regular upkeep and it was not enough. So now I am doing the slam and have some questions.
1. With a plaster pool, is there any danger in going above the slam level? I've seen warnings about the vinyl liners but not so much in plaster. I was wondering because I don't know exactly the capacity of my pool and would like to be sure I am not under slam level, but I also don't want to get into a dangerous regime.
2. Does it make sense to slam in recirculating mode? I am pretty sure I need to clean my filters but I am still learning about that and would like to start the slam anyway.

I am sure I have more questions but those 2 are the most pressing at the moment.

One more thing. I tested my cya a few weeks ago and it was 90. Today I tested again and it was 30. I thought that could not happen without draining ... Any ideas what could have happened (besides my own incompetence in testing)?

 

[JasonLion]

1) Plaster is fairly "chlorine proof", so you can go a fair bit above the usual levels if you really want to. But don't go wildly high, since you could in theory damage some of the other parts.
2) You have to filter at some point. In most situations now is just as good as later. But if you need to put off cleaning the filter, recirculate can be a handy way get by in the meantime.