Reading over your question it seems you feel the dog is protective of you. However dogs that are protective of people rarely act out like that unless they are taught to do so on a command, Truly protective dogs know where there is a real threat to the owner .
I am seeing some fear aggressive behavior however and some possessive aggressive behavior. If she h as issues when around food , she is likely possessive aggressive. This means anything she views as a value she will act out to keep it. Possession can be over food, toys. humans or space.
She may also have some fear aggression. Dogs with fear aggression will often act out at people on the property or walking near the property. They act out because they want to chase away what they fear. This works for them because they have no idea that the mailman was going to come and then go anyway. The dog thinks their actions caused the person to leave. Same thing with people walking down the street, the dog does not know they intened to keep going so it feels their actions protected them.
It seems the dog needs some daily training in a positive way. I would get a leave it command down so that your husband can give this command when the dog goes to bite the feet.
Leave it can be used for barking, chasing, going for food that drops on the floor and more. When taught 100% firm it tells the dog to stop what it wants to do and return attention to the owner to await the next command.
As far as the dog barking at the mailman or others, block off the line of sight from the dog so the dog cannot see them walking up until the dog learns its commands.
Play mind calming dog music to drown out outside noises.
Use an Adaptil calming collar and diffuser to help calm the dog.
You may have to keep a leash on the dog while you are home and until the leave it command is learned so you can prevent the dog from doing unwanted behavior.
Train the dog what you want it to do instead of acting out such as teaching a go to bed command and a quiet command, In order to teach quiet, you must teach speak first so the dog knows the difference.
Since leave it is a harder command to teach the reward for listening should be chicken or hot dog slivers.
If you have never used a clicker , you have to load it first before you start training. This just means you do 10 to 15 repetitions of clicking and treating so she knows that after the click sound, she is rewarded. The click sound, as you train, is actually a marker that she has done the right thing. The clicker costs about 2 dollars in a pet store.
Zac George -loading the clicker
Clicker training/positive method training/ print off
For more videos of clicker training other commands go to google search and type in “clicker training videos”
use a variety of items for training leave it so the dog knows it pertains to everything in its sight. Include using a remote control car for moving items
clicker leave it https://www.youtube.com/watch?v=zNAOe1djDyc
clicker maintaining focus http://www.clickertraining.com/files/auto-eye-contact.pdf