Have to agree with this - this is a LOT of points to purchase, and it seems as if there may be a better way.

It is hard to make alternate recommendations as you do not indicate the area in which you are going...but -

(for example) if you were willing to pay for some of the nights; you could purchase a $1K gift card under the Delta Bonus - it would cost you $900 - so you are $100 ahead AND you get points. (on both Delta and Marriott) I haven't looked recently - but at one point in time you could "buy" Marriott certificates with American Express points - is that an option for you? Did you check the MR award pages to see if there are any specials listed that you could use? When reserving a stay for this long; I often find that some nights are much cheaper than others - for ex a Sunday night is often a bargain. Did you pull rates only for the 14 day stay - if so, there may be less expensive nights out there. You could use points for the more expensive nights; and pay for the cheap ones.

Also remember that if you use points (bought or not) you do not get credit for that stay - so you are losing a bunch of nights that would head you into a higher level with MR; which means you can then earn bonus points on top of regular points.

As a newbie, I remember that I always thought using points was best - over time, I have learned that it is often a combination that saves me the most money...of course, it takes time to research the options!

Good Luck.