[Help] Any resources or advice to help me control my stubborn 5month old monster?

Since the day I got her (she was 3months old), she's gotten better. In the beginning she'd have food gaurding issues and would constantly teeth on me and pee all over the place. Now, we've almost got potty training under control, she doesn't grow at me if I try to touch her food and she doesn't bite me as much because I can usually offer her other toys and bully sticks which she'll settle for instead of my hands (most of the time.) The biggest challenge right now is her constantly picking things up from the floor and not releasing them. She knows drop it but only when I have a treat and only if it's to drop a toy or something she doesn't really need. When she doesn't wanna let go she gets mildly aggressive. A few examples: * Somehow there was a whole package of wonder bread on the floor of a parking lot. She grabbed it. She kept growling when we tried to take it away from her and then we ripped it from her a bit of plastic wrapping was still in her mouth and she tried snapping at me when i kept trying to take it away and eventually swallowed it out of sheer stubbornness. (i know it's out of stubbornness because she never eats plastic or non-food things otherwise. * She also got a decaying baby avocado that was on the grass when i was walking her at night and did the same possessive growling thing and would not drop it either * Has picked up gum on several occasions. I never knew there was this much spit out gum on the floor til she came along. This at least i'm able to pry out of her mouth because i think she regrets the decision once she it gets stuck to her teeth. * Literally picks up everything else on the floor like fallen flowers and leaves and sticks but usually releases it but she has to pick up everything just to try it * i also can't put on her collar or leash most of the time without her eating my hands the entire time.* she still barks/whines in her cage if you leave her alone in the room even if you cover her. for hours! The only time she doesn't do this is at night or if you somehow trick her that you're still there. I've been taking her literally everywhere with me because i'm not in a living situation where i can leave her alone all day to whine her heart out.I love this dog, I love her playful and energetic personality and I try my best to take care of her needs and give her plenty of exercise. When she's nice it's great but when she gets into these mildly aggressive states it honestly scares me and makes me lose hope because i've never dealt with a dog like this.Here's a pic of the adorable fluffy little terror via /r/dogs http://ift.tt/2ruTV24