IP addressing (internal & external), domains and multiple servers.

Hi guys, I would like some help from you network experts out there, I have a small knowledge but would like my project I guess to be sort of verified? Or approved to work would be the better way of saying it.

I'm hoping to run maybe about 4 servers, one being a small minecraft server, two being a web servers and the final one being file storage with a possible web interface or FTP, I haven't decided, but more than likely FTP.

I'm currently facing the problem of not having a static public IP address, though I may have found a solution by using a service that no-ip.com offers, which isn't explained extremly well on how it works although I have a somewhat picture of what I can use if for, a domain name instead of IP. I know that to run a webserver it's viable to have a domain rather than IP as it'd be easier to remember and navigate too for users, so firstly can I run a web server through a port other than 80? Also is there a way to stop my router from showing it's interface to the world as I don't fancy being hacked etc... If I type my public IP or public IP with port 80 appended to the end it takes me to the logon of my router, I wish to somehow stop that.

I do believe I could use a domain for people (well my friends as of now) to access the minecraft server, although I'm not sure if I could just give them my domain name to access minecraft server or if I'd have to make a new one and append the server's default port number (25565) or if it would communicate automatically through that port?

I have no idea about FTP or how to set it up so help here would be very advantageous The only thing I know here is that it's default port is 21 haha.

Also, I will not have enough RJ45 connection ports on my router and the machine will be a floor above and I don't fancy running a tone of cables up, but I do have a second router... I was thinking of connecting them via RJ45 and using the sub router, but my problem is that I believe the nodes on the sub router can make connections outwards but clients on the WAN ie WWW cannot make connections inwards. Is this correct? Or is it dependant on the setup? I believe this is referred to as subnetting?

Thanks for your time reading this, I know it's an unlikely question and such a long one, but I appreciate all the help and answers I receive... If any haha If I've made anything unclear, please tell me and I'll find another way of explaining it. Cheers all.