Yes, you can remove IPs manually VIA command line. Before you remove your server IP you should know that DA will not function, because it is licensed by IP.
If you are renting your DA license from a service provider ask them to change the license to the IP you would like to use, or if you bought it from DA contact their sales department.
How to remove the old IP:
1. Login as root to your server
Change to the IP directory
# cd /usr/local/directadmin/data/admin/ips
Remove the old IP
# rm -rf 212.199.8.101
Make your new IP the server IP
# vi 80.179.149.200
Use "i" to insert/edit.
Once you have finished your edit press the "Esc" key.
Then write and quite with this ":wq" then press "enter"
Make it look like below. You will assign the user and ns through DA.
Code:
gateway=
netmask=255.255.255.0
ns=
reseller=
status=server
value=
Then to fix your license follow this kb:
http://help.directadmin.com/item.php?id=30
Or simply forward the request to your service provider.
For your second question please follow this guide:
http://www.directadmin.com/newinstall.html
Your DNS for metaweb.co.il would be setup for you once you add your domain under the user-level, but make sure you have your reseller level setup first.