THis is a difficult time for you earlgrey. It is awful when you find that you are boxed into a corner by kids actions, and adult responses.
And we have all been there to a greater or lesser degree. Anyone who says they haven't is suffereing from selective memory syndrome.
You know, because of the fact they you posted on this issue that the situation can't continue. You know that this isn't in your best interests......or that of the kids. However much kids try to rule the house (and trust me they all try this at some time) in the end they don't want to be the boss.
They want you to the trhe boss. In the long term this will make them happier and more confident children. It will also help them to cope with school, and later in life, work.
It will be hell for a few days. And then it will be better. You have to get ready to make the change that you want. And I can see by what you have written that you do want to make the change. You already have the strenth of mind to see that. You have greater strenth than you know.
MN will be there to help, but you have already made the first step.