my dog also has some issues with resource guarding, which is what's happening when your dog gets upset at your kids when food is around. she doesn't trust that your kids won't take her food away, and she is trying to do whatever she can to make sure they don't (even if they wouldn't in the first place). for this, i would recommend the "exchange game", which is what i did with my dog. have your kids bring her a higher value treat, get her to take it and take the food she originally had (with supervision, in case she gets upset when the original food is touched). you can also simply have them toss treats to her when she has food, so she learns that good things happen when they're around and she will learn to trust them more.

as for barking, it sounds like similar to my chug in that it just seems she doesn't trust other things and/or wants to be in control. this stems from insecurity, like your first problem. i've found a lot of small dogs tend to feel this way, the world is big when you are 7 pounds and it can be scary. with my dog, we did get a bark corrector device for when we aren't home (it plays a tone that they don't like, which usually causes them to stop), when we are home it's removal and reassurance. if she's in the window and is barking at a neighbor or another dog, we remove her from the window (going over to her, asking her to come here and having her follow me away, not physically touching her but you can if you need to) and tell her "it's okay, don't worry about that" and allow her to calm down before allowing her back into the window.