You 100% can teleport Kroak on the vortex. Relevant part of the war scroll:
As long as the Balewind Vortex remains on the battle eld, the caster and the Balewind Vortex are treated as being a single model
from the caster’s army that uses the caster’s warscroll as well as the endless spells rules.
Using Great Rememberer to teleport Kroak into your enemy, casting all of his spells and then teleporting him back to safety is 👌
Also, have you tried a Thunderquake? The amount of damage the battalion can put out is insane and can surprise punk most heroes. I have gunned down everything from The Black Coach to a Vampire Lord on Zombie Dragon in a single round of shooting. Sounds like you have most of the pieces already too!