Right performance settings limit_req zone

Hello,
Hello, i just migrated from Apache24 to Nginx. OS on server is FreeBSD 10.3 (amd64) with custom kernel. I have one strange problem - when i uncomment this line in nginx config:

limit_req zone=antiddosphp burst=5;

then wordpress dashboard load take >2s then with this option disabled. Where could be problem? Almost every page take more time to load with this option (or i dont know how to right set this)...

My second question is about right perormance setting in config file. My VPS is

1x 2Ghz + 2GB ram + 15gb ssd

Free memory after startup is about 1700 MB. Do i have right settings for nginx? I also have postfix, dovecot, mariadb and php-fpm installed. Mariadb take about 200M ram, MTA take about 150MB so i have about 1300 free for webserver.

My nginx conf file:

load_module /usr/local/libexec/nginx/ngx_mail_module.so;
load_module /usr/local/libexec/nginx/ngx_stream_module.so;

user www;
worker_processes 1;

#error_log logs/error.log;
#error_log logs/error.log notice;
#error_log logs/error.log info;


events {
worker_connections 1024;
}

http {
include mime.types;
default_type application/octet-stream;

#log_format main '$remote_addr - $remote_user [$time_local] "$request" '
# '$status $body_bytes_sent "$http_referer" '
# '"$http_user_agent" "$http_x_forwarded_for"';

#access_log logs/access.log main;


limit_req_zone $binary_remote_addr zone=antiddosphp:10m rate=10r/s;
limit_req_zone $binary_remote_addr zone=antiddos:10m rate=10r/s;
limit_req zone=antiddosphp burst=5;

server_tokens off;

tcp_nopush on;
tcp_nodelay on;
sendfile on;

fastcgi_connect_timeout 100;
fastcgi_send_timeout 100;
fastcgi_read_timeout 100;
fastcgi_buffer_size 64k;
fastcgi_buffers 4 64k;
fastcgi_busy_buffers_size 128k;
fastcgi_temp_file_write_size 128k;
fastcgi_intercept_errors on;

gzip on;
gzip_min_length 1k;
gzip_comp_level 9;
gzip_types text/plain application/x-javascript text/css application/xml;
gzip_vary on;

open_file_cache max=2000 inactive=60s;
open_file_cache_valid 30s;
open_file_cache_min_uses 2;
open_file_cache_errors on;

client_body_buffer_size 8k;
client_header_buffer_size 16k;
client_max_body_size 20m;
client_body_timeout 10;
client_header_timeout 10;
large_client_header_buffers 4 32k;

keepalive_timeout 15;
send_timeout 10;
keepalive_requests 1000;


server {
listen 80;
server_name localhost;

location / {
root /usr/local/www/nginx;
index index.html index.htm;
}

#error_page 404 /404.html;

# redirect server error pages to the static page /50x.html
#
error_page 500 502 503 504 /50x.html;
location = /50x.html {
root /usr/local/www/nginx-dist;
}

}


server {
server_name test.test.cz;

#limit_req zone=antiddos burst=60;
#limit_req zone=antiddosphp burst=2;

access_log /var/log/example.com.access.log;
error_log /var/log/example.com.error.log;

root /usr/local/www/domains/test-cz/webserver/test;
index index.php;

location / {
try_files $uri $uri/ /index.php?$args;
}

location ~ \.php$ {
try_files $uri =404;
include fastcgi_params;
fastcgi_pass 127.0.0.1:9000;
fastcgi_param SCRIPT_FILENAME $document_root$fastcgi_script_name;
}

location ~ /\.ht {
deny all;
}
}


}

PHP-FPM configuration:

user = www
group = www

pm = dynamic
pm.start_servers = 3
pm.max_children = 3
pm.min_spare_servers = 3
pm.max_spare_servers = 3
pm.max_requests = 200
request_terminate_timeout = 10
request_slowlog_timeout = 0
slowlog = log/$pool.log.slow
catch_workers_output = yes

Thank you all for any reply.