Only time I got a company to lower the commission is when I was selling one contract and then buying another 500 points with them in two contracts. Pretty much I have always found is the same.
Probably not. Most charge 10-12%. And if it is a really small contract, they may charge you even more. I just sold a Hilton flex week timeshare and the selling company made more than I did on the sale. But I wanted to be rid of it; I just didn't want to owe them money on the sale.