Sorry for you, hope you can get this sorted with DF/Steam/HB and at least your friend lets you play it while this is being sorted.
Maybe Steam Family Sharing will work? (although it did not work for Wasteland 2)
Thanks for the empathy guys! I'll try to see it as an exercise in patience
After all, there are so many bigger problems in the world. I just learned today that the food produced atm would be enough to feed the entire world. Isn't that crazy?
Go Again to the link that HB give to you were you redeem the key, look!, there is a option to unlink the game (i think)
I can't find it unfortunately. Apparently the humble bundle account was connected to a friend's steam account (i changed it now, but the steam key is still redeemed to my friend's steam). The "unlink"-link to the right will atm just unlink my own steam account from the hb-account.