Anything outside of what the GUI (DA CP) can do, you will need to run yourself. May I suggest looking at RSYNC if you want to do the "timestamp" option? RSYNC can backup to FTP.
Its been discussed here before and if you search the forum you can find more details.
DirectAdmin is going to create the files with the same name every time. That cannot be changed by us.
One thing you can do is run a cronjob on the remote server to change the names after the backup is completed.
Another thing you can do is in advance of the backup create remote directories based on the date and then have the backup save to the dated directories.
There are a few options. You just have to have creative thinking.