I don’t understand the question. You’ve been a member for 3 years so I assume that you know how a lease payment is calculated and what the inputs are. If not, take a step back and learn that first.
This isn’t rocket science. Base MF, as much selling price discount as you can get, no extra fees, and max MSD. There’s no reason to be discussing cap cost or federal incentives with the dealer.
Get rid of the appointment. Throw their offer in the trash.
Go to edmunds and get rv/mf/incentives.
Research comp deals in the shared deals and marketplace listings to put together a target deal based on the pre-incentive discount target from your research and the lease programs as they apply to you.
Email them your offer.
Only go in to the dealer if they’ve agreed to your offer in writing and it’s to take delivery.