You've got questions, I've got answers!
1. Why does a recipe call for garlic powder over fresh garlic?
Could be any number of reasons. Maybe the chef prefers garlic powder, maybe the recipe is designed to be easy and quick (and powder is faster than mincing) or maybe it's a texture -- the recipe should yield something smooth not something with chunks in it. For example, I use garlic and onion powders in my mac and cheese recipe because chunks of onion and garlic don't give with how I expect mac and cheese to be.
2. What's a good substitute for oil in baked goods?
See my post(with a handy PDF chart) for baking without fat.
3. What other sauces besides tomato would be good for pasta?
4. What can replace "heavy cream" in a recipe?
Silk makes a soy creamer, and SO Delicious makes a coconut based creamer. Either of those should work. Coconut milk might also work, if the coconut flavor would compliment your recipe
5. I'm not new at being veggie, but I am new at reducing added fats. I love massaged kale salads, but my understanding is that they require oil. Do you know of any way to massage kale without oil?
I massage mine without oil all the time; there is also an oil-free "massaged" kale salad in HHC (pg. 181)