How to deal with a disorganized professor?
Talk to academic advising, or someone higher up in the department.
I applaud your efforts at being understanding, but keep in mind that teaching this class is his job.  Students not knowing what material will be covered, or how they will be evaluated on it, is him not doing his job.
It's certainly possible this professor has other things going on in his life that are preventing him from getting these things done, but they're very fundamental pieces of the job itself, and you're already three weeks in.  If he's incapable of doing this basic part, then the department should be involved, at a minimum to provide the professor with the support he needs.  And unlike in the spring, when the COVID crisis and at-home learning was suddenly thrust upon us all, we have had many months to prepare for it this time.  The same things that might have been excusable in April, such as scrambling to figure out how a class will work in week 3, are not excusable now.