So every time I pop over to Starlight I get a settler saying he's so hungry. Food looks okay, most of my settlements have supply lines, and when I talk to the settlers there are no complaints. I'm not sure what's going on. Any ideas?

Do settlers harvest the food? I have corn planted at a couple settlements but when I use the cooking pot there never seems to be any corn.

Shops. So I have shops. What are they good for?

Shops once staffed provide caps for you to take out of the workshop every so often. The higher tier the shop and the more settlers you have is more caps. Settlers complain about everything. "We really need to do something about the bed situation" is a common complaint even when I have 10 more beds than settlers.

Settlers harvest food. You can either assign them specifically or just plant it and they will default to harvest unassigned crops first. Settlers can harvest 6 units of food (eg 6 mutfruits or 12 corn stalks). There does seem to be a bug re: which crops get store in the workbench, it seems random. There is a helpful help feature in the game as well located in the save menu screen which covers a lot about settlement building.