Oh my gosh, Sherri. What a bunch of stuff to deal with!! We had to downsize before we moved to our place in a retirement community almost six years ago. We had about 30 years of stuff to downsize. It is a huge and overwhelming job. You have much hugs and sympathy here! Especially since I did not have the same other traumas you are dealing with. If you lived closer I would come over to help (I am not kidding, I am good at downsizing now!) But if you ever need a facetime/skype friend while you are in the process, I will be there for you!
Hard about your sister. Whether you are close or not, it is still traumatic. If you are close, it is the shared memories, if you were not close, it is regret that you were not closer. My mother lost her sister last October. They have always had issues (not major fights about anything, but they were never close). Loss is such a hard thing to push through, especially when it happens so close to the holidays. It is pretty fresh for you still.
Dealing with a parent with the issues you mentioned is hard under the best of circumstances. Having it disrupt your family makes it even harder.
And kids! Oh my gosh - kid issues are the worst to drag you down. You have so much sympathy here, I don't know what to do with it.
BIG HUG