If the WSFC role is down then this AG is down, if the cluster goes down (did you configured any witness) all AG on that cluster goes down. I don't...

Try dmv sys.dm_hadr_database_replica_states and just join them:

DECLARE @MyDate DATETIME = '21 March 2018';
WITH LastBackupCTE (DbName, BackupfinishDate)
AS
(
  SELECT database_name,
    MAX(backup_finish_date) AS BackupFinishDate
     ...

There is no magic, if you don't make overcommit on host, vm should work OK.

General best practise is:

1. paging file: default, mssql try dont use paging file, but may be...

No, you should see the endpoint for mirroring. There was no errors during creating endpoint? Are you sure that something is listening on endpoint port? Do you have multiple instances...

Endpoints are started? Can you telnet on the endpoint port? Name resolution work correctly?

Log in tempdb behave like log for db in simple recovery mode. Checkpoint fire when log is in 70% full and then clear the log. You can execute manually checkpoint...

You can't edit data in mirror db. If you disable the mirroring session and bring db online then there is no mirror 🙂

You can't edit data in mirror db, so booth questions: not aplicable.

eg. http://download.microsoft.com/download/7/3/c/73cad4e0-d0b5-4be5-ab49-d5b886a5ae00/sql_server_2012_licensing_reference_guide.pdf or just google: mssql licensing guide.

From SQL2014 license version you must have Sofftware Assurance for passive node.

Not the same problem but show a few things you should worry about http://sqlperformance.com/2012/11/system-configuration/2012-cal-problems

To workout with numa imbalance and spread schedulers evenly you can try set affinity cpuid from 0-7...

But why put SSIS in DMZ? SSIS don't serve any content, you dont need to put it in DMZ to connect to any source or destination.

Like all other services, block all ports on the internal and the external network and allow only explicit ports. But why you want do this? Cant find any reason to...

Nice to have, but costly 🙂 $931 (Standard Server) vs $8,908 (Business intelligence Server) and CALs (circa 200$) for each user/device https://www.microsoft.com/en-us/server-cloud/products/sql-server/purchasing.aspx, simple math.

For standard you have a option...

But they have totally different features, if you don't need the BI features then Standard + CAL will be cheaper, if you need these features then you can compare Enterprise...

No, minimum for server/virtual machine is licenses for 4 core, downgrade rights are part of volume licensing, you can read details in Product Use Rights (PUR). http://www.microsoft.com/en-us/Licensing/product-licensing/products.aspx

http://sql2014.pl/docs/SQL_Server_2014_Licensing_Guide.pdf

http://blogs.technet.com/b/volume-licensing/archive/2014/05/29/licensing-how-to-sql-2014-licensing-changes.aspx