I just don't understand how people can be like that, really... OBVIOUSLY you have more things on your plate than can be humanly possible to deal with. I really hope you are doing well, health/sanity/finance wise...
(I'm not going to bother you with any commission info just yet, I'd like to see you get more caught up on things before you have to deal with me! I'm still interested in a sculpture somewhere down the line... when time permits!)
Have you tried organizing your notes into folders, and deleting the ones that aren't as important? Maybe you could make a folder for "To do" and "To answer", and then delete them as soon as you are able/have done what was needed?
A commission journal might help with keeping people in the know of how things are coming with their piece, especially if there are multiple people waiting for something, they'll at least have an idea that they have a wait ahead of them due to whatever reasons, such as they are so far down a list, where you're at on working with it, etc.
Though in regards to the angry notes journal, you could send off notes to the commissioners every so often yourself, to let them know that such and such is going on with their requested art and you. I do this myself for larger pieces or when something starts getting in the way of the art being done. At least this way those on my list know that I'm not ignoring them or putting their art off, and that I do have to put my life/school/work first. It just keeps everything on a better note I find. It sort of generates a feeling of mutual respect for both parties.
Though I have no doubt that you're a very busy person, this might not work for you very well, but checking in with commissioners maybe once every two weeks I think would probably help keep things cooler with a few folks perhaps?