Doubt with ngx_http_limit_req_module

I have a doubt with the directive "limit_req_zone" on "ngx_http_limit_req_module".

In this example we can see that the "shared memory zone" was set to 1MB (1048576 bytes):
limit_req_zone $binary_remote_addr zone=one:1m rate=1r/s;

If every "session state" use 64 bytes, this means that can I save 16384 IP's (1048576 / 64), and after every request returns a "503 Error"

My questions are as follows:
[1] Is posible know how much memory are using or how many requests are saved, to know if the memory asigned is not enough?
[2] If I restart or reload the nginx service this memory are cleaned?
[3] This information has a life time?

I'm worried about reaching the limit and that my website start to return 503 errors to everyone.