Hello.
It is not possible to delete anything on the blockchain. It stays recorded forever. The only thing that you can do is superficially delete the body of the post on the front end.
I do not know why you cannot vote as your voting power seems to be at 100%. It is not possible to prevent anyone from voting unless their power and resources are depleted.
You can see the state of your account here:
https://hivetasks.com/@bastelwastel
Maybe there was some frontend bug. Try using different Hive frontends to log in like hive.blog, peakd.com or ecency.com. All use the same posting key.
I see that these downvotes on your posts have been retracted by now.