Scheduling the run of the stored procedure is something you do using a SQL Agent Job.   The SQL Server Agent Service runs under the security context of its "service account",...

So, it worked then?

Runs fine on my machine.   Not sure where the trouble is...   Any chance of an accidental keystroke that messed with your copy after you pasted it into SSMS ?

Might want to try it this way:
DECLARE @command AS varchar(2000) = '
USE ?

PRINT ''--=========================================================================='';
PRINT ''USE ?'';
PRINT ''--=========================================================================='';

DECLARE @note AS varchar(2048), @id AS...

I think the cart has come before the horse.   I suspect what is needed is that the cursor SQL needs to be the contents of the @command variable.

EDIT:...