Seller Gives "Best & Final" Offer

[Jeff Cross]

Looking for some some input on my negotiation status. After my initial offer, the seller countered. I countered his counter, then he responded with a "best and final". How appropriate is it for me to respond with MY best and final? His best and final is about 1% higher than my max. Would it be acceptable to ask for seller to pay for all or even just a portion of closing costs/prepaids? I want to be respectful of his best and final, but I really want to see my overall cost drop another 1%. Thanks!