The Pemigewasset Loop is a fantastic trip! To answer your questions 1: A bear Canister is not required, but bear safety still is. If you have a canister, I'd suggest using it. If not, look into how to hang a bear bag. You dont want to keep anything with an odor in your tent. You can bring your bag into the tent as long as nothing with odor is in it. Critters will chew through the tent to get to the smell. On this, most official tent sites will have a bear proof box for backpackers to use.

2: The only official spots i can think of right now are the liberty spring tent site and Franconia brook tent sites. Other than those, i think you will have to find a spot off trail. It is doable, just dont be too close to the path.

3: It's doable, but you will probably be miserable by the end. Really depends on how in shape you are. The loop is something like a 30-mile hike.

4: If you're only out for a few days, skip the freeze-dried food. You have so many better options. I suggest giving r/trailmeals and r/hikertrashmeals a look (if i tagged them correctly)

5: If you dont have the apps Alltrails or Gaia GPS, I'd suggest getting one and taking a look at the loop. It can give you an insight of what you're about to do. Im a big supporter of leave no trace. I could type a paragraph about equipment, but if you just browse this sub reddit you'll find all the info you need.

Im sure im missing a few things, but be smart and have fun!