Based on the wording of his card I assume that it only matters if the hull zone he targets has shields or not. If the target redirects to a shielded hull zone that won't prevent his re-rolls from happening. It only matters if the initial target hull zone has no shields.

Does that interpretation sound right?

Correct.

It is the "Defending Hull Zone", which is what you nominate as your Target.

Redirects simply change where the damage goes, they do NOT change the Defending Hull Zone.

And can he only rerool one time per shot. I only as because the cards are normally so detailed I questioned it just becuSe it doesn't say one per attack or activation

Correct. This is how XI7 Turbolasers works as well.