Letter13

You can add a reply to an existing open case.
You shouldn't create additional/multiple tickets for the same issue, however.

This is something you would need to reach out to DE Customer Support about. I don't think anyone on the forums can give you a definite answer on whether it's safe to use or not.
That said, if a keyboard of mine was experiencing bouncing issues on keystrokes, I'd probably get a new keyboard. Preferably one with a working debounce circuit to prevent such issues, rather than rely on an applet to address faulty hardware.

You can contact DE Customer Support to see if they can remove/unlink an account from your cross-save account, though they may get back to you with the answer that it may not be possible. As far as I'm aware, account linking is permanent and any linked accounts not set as the primary account will be overwritten.
When the android version comes out, I imagine you could just link your android account to your cross-save account to bring your account progress to that platform, the same way if you picked up a console and wanted to use your cross save account there (by linking the console account).

If you make a new account and don't violate the EULA/Terms of Use further, you'll probably be fine. The clause about 'making alternate accounts to circumvent restrictions' has more to do with using alternate accounts for exploiting (i.e. riven space, trade mules, bypassing ignores set on you by other players, etc) or for circumventing forum restrictions (i.e. forum suspensions, moderation queue, etc).
Making a new account after your main account is fully banned from the game isn't really 'circumventing' the ban because your original account with all of its items are still banned and cannot be accessed.
However, DE Customer Support has the final say on a matter like this.