I want to book an award for a 4 night stay which according the web site will cost 70k points. I will have 63k points in my account by the end of this week and do not expect any more points before my award stay.

How can I make up the difference?

Are any discounts in points level given to silver members/ can I buy points, if yes at what cost/ what is the transfer ratio from Amex to Marriott?

Thanks in advance.