I am wondereing where the boys may be learning the reactive behaviors. Children learn from modeling-what they see another do. We can lecture our kids about right and wrong until we are blue in the face and they will still learn from modeling first.
You made a reference to Toy Story: How much tv/movies are they exposed to? Is anyone else in the family impulsive/reactive when they are under stress? Are there any friends or other family members that are reactive and especially physically so? How do you and your husband deal with your own stress? It sounds like you have a lot on your plate: Are you finding yourself shouting at the boys or grabbing them or spanking them out of exhaustion and being at your wits end? How are you resourcing yourself (self-care) through all of the things you have going on?
Sometimes we don't even realize where we are showing our kids how to behave a certain way. Often we are not conscious as to all the things they are actually being exposed to. Disney movies are fun and also filled with violence as are a ton of our tv shows.
I am one to start questioning all the things both internal and external that may be effecting myself or my children. Do your boys feel a great deal of pressure to "be good", perform well, sit still for long periods of time, or anything else that feels like stress to an active 5-year old child? What tools do they have to help them release stress? Some examples might be: yelling in a pillow, coloring a crazy, scribbled picture, running around outside, having permission to say no, etc.
"Threatening to take toys away" could be an example of where discipline is not followed through. If you establish that if a certain behavior happens then a certain consequence will happen then it needs to happen every time. Threats are meaningless to children.
Like you said, they know how to push your buttons. That is what kids do, however, as much as it feels like it, they aren't doing it "to" you. What the button does is turn on our old tapes about our own unresolved "stuff". It was my greatest challenge to be aware it was MY issue they were triggering and therefore I needed to deal with that seperately from my disciplining. The book 1-2-3 Magic helped me to understand that process for myself. I learned to zip it during a confrontation with my kids, follow through with the consequences, and then go and deal with whatever issue had been triggered for me. In support of You, T.