How to hide the port number on a home installed wordpress?

I hope someone can help me out. I may be doing this incorrectly or overkill, please bear with me, first time to use wordpress.

I installed wordpress on a Synology NAS on my home webserver.
Unfortunaly, my ISP blocks port 80 so i had to use another port number.

I also bought a domain from DYNDNS and used the webhop feature.
In summary, the way i can access my wordpress outside home is:

1) I type “http://mydomain.net”
2) Dydnds.org automatically redirects this to my dynamic IP address and adds the port number i defined. so it becomes (for example:)
“http://59.60.61.62:5000” or effectively, this is also the same as “http”//mydomain.net:5000”

3)So all is ok. i am able to use,post,edit my wordpress from outside my home or when i am in the office.

4)My only problem is, i do intend to make my WordPress public.How do i hide the port number “5000” on permalinks? Even on google, when i searched my website, i saw the result and the links posted contains the port number “5000” ..

I tried fiddling on the Dashboard, General— to change and remove the port number but it crashes or i get page cannot be displayed when i view my wordpress.

So it was hours of work lost already and i had to reinstall wordpress for the nth time while im trying to figure out how to do this. I can’t find any example in google. but i would appreciate if you can point me the right direction.. please.