It is obvious your current dealer is not budging with the numbers so If I were in your shoes, I would contact the dealer with the car I want directly. I would let them know the terms I want (e.g. 36/10), the MF I am looking for, and the final sale price I am targeting for a specific MSRP (e.g. 5% discount over MSRP). I would also assure them that I would sign immediately if the numbers are met.
Let’s see what they come back with. I would negotiate the final deal. If numbers make sense, I would go sign the deal, bring the car home, and once I have all the documents, would buy out the car.
Obviously, I would do the buyout calculation beforehand to see if everything lines up properly and what discount I would be getting.
I know that the MF wouldn’t matter, and neither would the RV but I would still feel better if the dealer uses the base MF.
Others who have done this could answer this better. I believe people have already answered this in the current thread as well as here: