Can you build up a new server ('name_new) and then when ready to migrate, rename the old server to 'name_old', then rename the new server to the existing server name? ...

Window function is another way:

-- Selecting Duplicate Records
With CTE_Employee
AS (Select Employee_ID,
           Employee_Name,
     ...

We have a patching system, it will execute a 'stop' before restarting, I see those in my logs during our company's maint window.  Do you have some kind of patch...

Enable the DAC so you can get in and see what is running when it locks up (sp_whoisactive).

https://www.brentozar.com/archive/2011/08/dedicated-admin-connection-why-want-when-need-how-tell-whos-using/

Did you try right clicking on the database, go to options, and set the Read-Only to False?

DBATools is awesome for this:  Invoke-DbaDbClone

About the only time I see something like this is when I grabbed the wrong backup (an older one).  You are certain you grabbed the correct backup file?  Did you...

If the issue isn't DNS it's probably a Kerberos\SPN issue:

https://learn.microsoft.com/en-us/sql/relational-databases/native-client/features/service-principal-name-spn-support-in-client-connections?view=sql-server-ver15

You can use the MS Kerberos tool to check it:

https://www.microsoft.com/en-us/download/details.aspx?id=39046

Also, is the SQL Browser Service running?

Shouldn't it be IP, port   (comma not colon) ?

Rollbacks are single threaded so it can take much longer than than the parallel operation that got you there.

I would give 'dbcc updateusage' a try.  I can tell you this has fixed weird disk performance on new servers for me more than once.

https://learn.microsoft.com/en-us/sql/t-sql/database-console-commands/dbcc-updateusage-transact-sql?view=sql-server-ver16

#1.  Since nobody has responded, I'll offer maybe a bump in the right direction.  I've found SPN's are very important to SSRS.  I'd make sure you have a domain account...

In AD, did you give the service account the 'Trust for delegation'  property?

https://dbatools.io/    - makes this very simple

You can use 'Sync-DbaLoginPermission' (everything) or 'Export-DbaDbRole' (to get role)

Shrink it in smaller chunks.

Google for a script to reduce it incrementally.

https://www.sqlservercentral.com/blogs/sql-database-incremental-shrink-tsql