Connecting to www.directadmin.com[216.144.255.179]:443... failed: Cannot assign requested address.

This would imply that the IP that was specified for the install is not a valid IP address on your machine.
If you are running a LAN, or behind a NAT, with a different IP on the machine than would be visible from the internet, then use the lan.php guide

You can test out the command by running:

wget --bind-address=1.2.3.4 http://www.directadmin.com/index.html
wget http://www.directadmin.com/index.html

where 1.2.3.4 is the IP address in your license file.  If you get the same error with the --bind-address option, then that IP is not present or valid in your network device.
The 2nd wget command should work from within a LAN.
If both fail, then it's some other issue (firewall, network, routing, etc..)

You can run

/sbin/ifconfig

to see what IP's are present in your network device.  Make sure the IP in your license is present somewhere in the output.

The IP in your license file *must* be present and working in the network device.