yes, lets see a cluster validation report please

Please this Microsoft knowledge base article for more on mirroring and log shipping combined together

https://technet.microsoft.com/en-us/library/ms187016(v=sql.110).aspx

all 3 nodes must be a member of the same windows server failover cluster, confirm this please

Time to re visit the database design, normalisation wouldn't go amiss here.

The script itself uses 4 variables of 256 each but the dynamic sql variable is only 999 and mixing...

a cluster should have an odd number of nodes ideally, you would then use Majority Node Set quorum.
If you have an even number of nodes across multiple data...

Good attribute but needs to cover a bit more in depth especially around DNS.

My stairway level on mirror traffic segregation can be found at this link

http://www.sqlservercentral.com/articles/always+on/131901/

virtualisation has an overhead, average 10-15%, what ever way you dress it up. There is a software layer interracting with the hardware, the most sensitive and usually the worst performing...