I agree. The first to go would be the butter and the fat in the nuts going rancid. How long can you keep butter? Being mixed up it probably wouldn't last as long as a block of butter, but if it's airtight it should last at least a week, probably longer. Because you don't know what bacteria might be in it just from mixing and packing, it's important not to sample it raw. Bake it up when you can, and freeze the extra cookies if you can find the space.

Leavening/soda makes dough rise. Proving/proofing shows that the yeast is alive (not an issue with dry granulated yeast, but absolutely necessary for cake yeast and starters). Rising is what the dough does. Commercial bakers nowadays proof yeast in the dough while it rises because the yeast is so reliably alive that they skip the step where you feed the yeast and make sure it bubbles up before wasting a batch of flour on it, which is the original meaning of proofing your yeast. They just look at the risen shaped loaves to see the proof. This has become so prevalent that bakers are using the word proof and rise interchangeably. You raise your hand and your crops, and rear your children. :)

I don't see any reason why not. I might let it dry out first so it could be easily broken up into crumbles or smaller particles that could be more easily buried with other material rather than leaving in a big clump. And I would make sure it was well buried or incorporated into the pile so as not to attract critters.

"I am going to try freezing shortbread and oatmeal raisin. I read that they work well." No problem at all; I do it all the time. I freeze most cookie doughs with great results, including shortbread, sugar cookie and any type of oatmeal or other drop cookie doughs. Right now I have a lot of cookie dough in the freezer, including shortbread, sugar cookie, oatmeal/cranberry, gingerbread and molasses. What I wouldn't freeze are more delicate cookie doughs that have more liquid and are thinner, such as florentines and tuiles. Sooz, freeze away! I agree with plllog. Snickerdoodle dough freezes beautifully but add the coating right before baking.