How do I give away a game that is not in the gamelist?

As long as the winner gets what the giveaway is for you're fine. In this case since you cannot choose the bundle you can make a giveaway for the base game and note that it is the RAD Edition in the description. Alternatively you can ask support (may take quite some time to get a response) or ask in the humble choice january thread.

I believe you could create a ticket (under the support tab at the top) to ask for it to be included in the giveaway list (although I'm sure many people have done this already) or you might just have to create the giveaway for the base game and say in the description that it comes with the DLCs :) If you decide to wait to see if it will be included in the list soon (I'm sure it will) be warned that people can enter just for the DLCs even if they have the base game already, it's up to your discretion if you want your winner to be able to enter only for the DLCs or you can reroll the winner before you send the key if you see they have the game already!

You cant create giveaways for steam bundles. Only if its a sub. Just use the normal appid.