Is there another way to purchase the full version?
Steam blocks anything NSFW in Germany since the end of 2019. It's the same with your game. I can't even see your devpage.
Sorry for the disillusion. This doesn't help, if Valve simply blocks your connection if you use a VPN (first hand knowledge).
And you can believe me they are pretty good at detecting this. The original accounts are locked to the location that is associated with your payment information and new ones can't (/almost can't) be created via VPN because in 99% of the cases they'll know it is a VPN you're using.