I would also use SP_WHO_ISACTIVE, to see what is currently using resources.
Always a good starting point.

Does the account that is running SQL SERVER SERVICES have permissions to the Windows file or folder.

Hi
In an ALWAYS -ON setup only user databases are synch'd across to the secondary or secondaries. The system databases are not shared in this environment. You have to think...

I use it everyday and just use the server name and not the listener name to register in CMS. As they are separate servers and need to be queried individually...

There is a link to MS in the link below.

https://social.msdn.microsoft.com/Forums/sqlserver/en-US/88d67309-aef4-401e-963e-f85a76c9d33c/sql-server-2012-alwayson-multiple-instance-multiple-listeners?forum=sqldisasterrecovery

I think I read a while back about instance stacking and the default port for the LISTENER, I'm sure best practise states that the default port for the  Listener on...

Can you make sure the DNS name is being used for the LISTENER connection in the 1st Script.
select * from sys.availability_group_listeners

SELECT
AG.name AS [AvailabilityGroupName],
ISNULL(agstates.primary_replica, '') AS...

To be honest I haven't really read your post properly, but from scanning I think you maybe looking for this.

USE Master;

GO

CREATE TABLE [dbo].[#TmpErrorLog] (

I think you know what you have to do already.
Just TEST and make sure all is well.

Is the identity column and Identity (1,1)  column if you script out the table.
I think TRUNCATE is your best option, but test first.

If you go to the...

Do you need to keep any of the data in these tables?

https://dba.stackexchange.com/questions/2247/how-to-set-full-text-catalog-location-sql-server-2008-2012
Found the above on Line

You need to run that script at the time the log is growing, or the process that is growing the log is running.
Hence logging it to a table, if...