1. If a recipe contains sour cream, mayonnaise, cream cheese, melted cheese, or (cooked in some form) eggs, can you freeze it?
A: In my experience, Yes. I freeze quiche and cheescake okay.

2. Are mushrooms, garlic, olives, pickles, within a recipe okay to toss in the freezer as part of the leftover?
A: Of course!!

3. Is it dangerous to fully- or mostly-cook meats and freeze and then take them out and finish cooking them later when you want to eat them? 4. How long can you freeze foods that have eggs or dairy or melted cheese? Or is there no real time limit on any freezing as long as it stays frozen?

Meat should be frozen either raw or completely cooked. Partially cooking meat and freezing may allow bacteria to breed when cooking is completed. If meat is fully cooked, and then you toss it in a frypan to warm it up it should be ok - as long as you are not completing the cooking process. Be particuarly wary of chicken.

For the same reason NEVER deforst meat in the microwave that you aren't going to cook straight away - microwaving at defrost setting will partially cook the meat.

6. If something has got ice crystals all over it inside the bag and looks like it's getting "freezer burn" is there any solution to this short of eating it immediately or throwing it away?
Freezer burn can be cut off. On chicken the freezer burn area's are grey, and can be cut of before cooking. On other food stuffs it is harder to tell.

Remember, not all icecrystals mean the food is freezer burn.

I mean would rinsing it off, then wrapping it tightly in butcher paper and bagging, and putting back in the freezer, be ok to 'salvage' it?
Makes problem worse. Becuase it is wet, then that freezes.

7. Maybe this is a stupid question. I never see salad frozen.
You CANNOT Freeze lettuce. I don't know why it doesn't work, but in my experience it wilts and goes dark when defrosted in fridge. It's also near impossible to not freezer burn.