Setting Web / FTP Home Server With Netgear DGN2200 And Zyxel USG100 With Firewall

I want to public to the internet a web + ftp server, all running in the same machine that now is a performance pc, in the future will be a qnap nas ts-220. I don't need extreme performance so my ISP gives me only 12 Mb down and 0,8 Mb up. I will use the nas as download station, ftp server and a web server when I'll public a personal site.

this is the config:

-modem/router adsl2+ that connects to the internet. ISP gives me dynamic ip! it has 192.168.0.1 ip and I think it cannot be changed.

-a firewall hardware zyxel usg 100 with all active UTM services. it has default ip 192.168.1.1. the netgear in the "attached devices" see the zyxel as 192.168.0.2, the same ip zyxel says to the wan1 port.

-a pc or, in the future, a nas that now has automatically assigned ip 192.168.1.34.

I must use a free or paied service as dyndns or something else. If the solution to retrieve everytime the dynamic ip is to set the ddns only in the router/modem netgear then it can only use dyndns.org or .com or .it with the dns of the associated ddns service. For example: if I set a dyndns.it account in the netgear I must set also the dns provided by dyndns.it because if I set google dns or something else the service cannot work.At the moment I tested only with a filezilla server running on the pc directly connected to the netgear, no zyxel in this test.

The config is:

netgear with ddns service provided by dyndns.it, activated with the username and password, in the wan I setup the dmz as 192.168.0.2, in the adsl settings setup the dyndns.it IPs. in the services of the netgear also provided a custom service with ports from 60000 to 60050 and created two rules one for outbound and one for inbound where I let data pass from the wan to the server in the lan 192.168.0.2.

filezilla running on the pc with windows 7 x64 with lan ip 192.168.0.2 mask 255.255.255.0 as th3 netgear and gateway of course the netgear 192.168.0.1. dns servers same as provided by dyndns.it. filezilla configured with only one anonym user without password for testing, default listening port is 60000, passive mode active with range 60000-60050 and for retrieving IP I set default, no Dyndns.it host cause it will not work.

So configured it works fine!problem is when I connect the zyxel between the netgear and the server.how change the default ip of zyxel? in configuration - ethernet - lan port is correct to set there the default and static ip to 192.168.0.3? there are many options! same as dmz you can set there the static ip and what ip?also when you want to public a server zyxel don't say nothing about port-forwarding. it says only create two address objects one with ip of the netgear and one with the ip of the dmz port then create a rule in the firewall section where you set wan to dmz and destination and origin ip selecting the two address objects previously created then you are ok...no, really no! and the ip of the firewall rules in the netgear? which ip do you must set? 192.168.0.2? or 192.168.0.5 if you set it up in the dmz port of the zyxel? no, it is a conflict so you must set another ip.to set correctly the server to be visible in the internet with the netgear + zyxel usg 100?