Killed Backup in Rollback State for Days
Since the backup is waiting on a CMEMTHREAD, that is a critical section waiting for a memory allocation, it is likely that a restart of the service will either allow recovery to start on the database, or for the database to be marked "suspect", at which point you could drop and restore from backup.  Recovery on a 70MB database, assuming the log file isn't many many gigabytes, should be nearly instantaneous.

As always, before doing anything of this nature, you need to ensure you have verified-good backups of critical databases on this instance - by "verified", I mean you've restored them onto some other server (or your workstation), to ensure you can actually perform a restore.  There is nothing like getting free advice from the internet only to find you've lost everything.

As an aside, you should ensure you have the most recent service pack and cumulative update installed on your SQL Server; see SQLServerBuilds for details.