QIf this follower gets Storm from its ability when I put it onto my field, and I declare an attack with it on the same turn, but then the total number of cards on the field drops below 8 for some reason, causing it to lose Storm, does the attack still go through?

AYes. Even if a follower loses Storm during an attack, the attack still goes through.

QIf the total number of cards on the field drops below 8 after this follower is put onto my field, does it lose Storm?

AYes, it does.