I don't have any specific knowledge of Marriott Disney France but I have a few thoughts:
1. The TDI of the period that you are interested in, is 150, or the top of the scale. That boils down to the demand being a lot higher than the supply.
2. Marriott France is usually a pretty easy trade during the lower demand periods. I also sometimes see it for very reasonably priced getaways. Also I'll see 2 BR units when searching with a 1 BR. But I think that most of these availabilities were not in the high demand period.
3. I've heard that a lot of Europeans go "on holiday" during the July-August period and that a lot of restaurants, and stores have minimal staff during that period. This translates into poor service or at least longer waits.
4. You have good trading power using a 3 BR (especially if you would accept a 2 BR). But even though you have good trading power, you need someone to deposit their week.
5. If you have the flexibility to travel earlier or later in the year, I think that you may enjoy it better. July/August weather can be warm and humid. Occasional thunderstorms. I've traveled to France during just about every month of the year, but I especially enjoyed May and June as well as Sept. and Oct.
I'm hoping that others with specific exchange experience will chime in to better help you.