Sellers can not contribute towards repairs after settlement. The sellers must make any necessary repairs to satisfy lender requirements. If the lender does not have any requirements for repairs, then you will have to negotiate with the sellers to make any repairs you want prior to settlement.
Finally, you can not get any cash back (except your escrow deposit(s)) at settlement. For example, if you negotiated the seller to pay $5000 towards closing costs and needed only $4000, the seller keeps the $1000 you did not spend. Make sure you spend more than the seller's contributions towards closing costs - and yes, you can buy points to lower the interest rate.
I think you might mean "credit at closing to be applied towards closing costs and prepaid items". That would be a maximum of 6% of the purchase price. You will not actually receive any cash back at closing. Your agent will know how to write it up.