You can join here Bitcointalk Party - Discord server and asked Cyrus to attend to your request since he is also an administrator. I bet his active there. Maybe theymos is busy.
Other option:
Request for change name to theymos to alter the username. Also regarding your posts deletion, why not hired someone to delete it for you manually. Post it here Services maybe some will be interested. Just a suggestion might work for you.
For 4500 post well, good luck for manually deleting it , I don't see any issue of deleting the post you already made here, just leave the forum for good and don't visit this site again. you don't need to delete all of it, as if you are using your real name in the forum and you don't want other people know that you are once member of bitcointalk .
And for manually deleting post you can't also delete a post made on the locked thread so even you do it manually There are still posts left that you can not delete .