You're very close to making this deal happen. You have an interested buyer and a willing seller and they are only $2000 away, not much considering the scheme of things.
The definition of negotiation is not finding a middle ground,that's compromise. Negotation is getting the other party to do what you want by giving up other things that you don't care about. Think of the other things in the contract that can be negotiate besides price. Things like closing costs, repairs or buying "as is", closing dates, etc. Also, don't forget there's a second round of negotiations after the home inspection.
Keeping in mind that this is your buyer's offer and not yours, what things would the buyer be willing to give up to get his price? What things would the seller be willing to give your buyer to get his price? Buyers like to feel like they got a great deal. Sellers like to feel like they got top dollar. There are also other motivators that you need to figure out so everyone walks away feeling like they got what they want. Not that your job is to make the seller happy because it's not, but you do want agreeable parties.
Hope that helps.