with Comcast I have a modem with 2 IP(s) and the LAN is connected to the modem and receiving the 2nd IP, so the incoming connection from LAN and WLAN (comcast wifi) considered as private network?
Huh? You lost me as to your actual topology there.
Private IPs are just RFC1918: 10.0.0.0/8 172.16.0.0/12 192.168.0.0/16
If you are connected to something outside your WAN, are receiving an RFC1918 address and are not NATted to a public IP, and attempting to make a connection into your WAN to a port forward then yes, you need to turn off block private networks on your WAN.
Blocked connections from the private IP should show up in the firewall logs.
When inside your network does your server DNS resolve to internal or external IP? If external, you need NAT reflection.