Of all the things you listed, I don’t see you contacting Netflix to see if they have a solution to your Fios promotion. They may have had more than one snafu with Verizon over this.
fios is not going to credit you. However you may have grounds to cancel your service under not receiving your inducements under the promotion.
you could also contact your states attorney generals office and file a charge with them.
you will need the complete offer and web portal links and the links that don’t work for redemption. Copy only to this state agency, no originals.