You've got questions, I've got answers!
1. My husband has been concerned that we're not getting enough calcium since switching to a vegetarian (trying to be vegan) diet. He's run some numbers to compare what we're eating to see how much we are getting each day, but still feels like we aren't getting enough. What are your thoughts and suggestions?
Calcium is in most whole plant foods, so as long as you're eating a healthy, varied, plant-based diet you should get MORE then enough on a daily basis. Plus, even non-wholesome foods, like soy milk, are fortified with calcium. It would be hard not to get enough unless you just eat junk all day which I know you don't :-)
See this link of the world's healthiest foods. Make sure to include those plant-foods listed, like greens. You'll get more than enough. Interestingly, eating dairy actually causes calcium to be leached from your bones, so you'll get more or at least, retain more calcium, by eating plant-based.
2. Why is nutritional yeast used in recipes?
See my post (and video) on nutritional yeast. Normally, it gives foods a cheesy flavor. I love it!
3. I like the seasoning packets at stores for convenience but have noticed some contain junk ingredients, can I make these mixes myself?
Absolutely, there are tons of recipes online for replicating seasoning packets at home -- get Googling!
4. I'm still apprehensive of tofu! What's the difference between refrigerated tofu and Mori-Nu tofu?
They are the same (as they are both tofu) -- except Mori-Nu sits on a shelf in a juice box container and the other must be refrigerated. However there are different types of tofu -- Mori-Nu is soft, like pudding, and the refrigerated kinds can be soft, but they can also be firm and extra firm... see my big tofu post for more info on the types of tofu.
5. I've tried to make your "chicken style seitan" (p.142, HHC) and "pot roast seitan" (p.133, HHC). Both times they came out delicious, but too chewy. The pot roast was almost as chewy as gum. What can I do next time about the chewiness? I'm very new to cooking seitan and have never had it before trying your recipes.
Sounds like over mixing or too much kneading. Seitan can be a challenge, I admit.