His FTP is working; I just tried it.
He recently changed the user name and password for it, so make sure you're not trying to log on with the old ones.
I haven't tried Sonic Adv. with the new NullDC either, just the old NullDC 1.0. So, I don't know if/how well it works with nullDC 1.6:
For the old NullDC 1.0, you need XPadder:
http://www.xpadder.com/
Click the green arrow on that page to download XPadder.
The new NullDC 1.6 now has gamepad support.
Options > Select Plugins > for Maple Input, choose NullDC Joystick.
Then go to Options > Maple > Port A > put a check mark next to your gamepad > then click Config and set your controller.