How should I handle disinterested/unorganized adviser?
Advisors are not expected to be perfect but they are expected to do their job. Yours doesn't, he's endangering your PhD and his institution (probably his career too but that's not the point).


  Is this a typical scenario?


No. 

Sure, some researchers are disorganized, have a messy office and/or hard drive, it's quite common. Some advisors are also known to occasionally abuse their role and give their students jobs which aren't related to their PhD, that's frowned upon but often tolerated. But whatever their shortcomings, an advisor must be able to fulfill their professional duties, and your advisor doesn't. 


  Am I overreacting?


Not at all.

Contact the head of the department, the institution ombudsman or whoever is in charge. It's not too late but it's time. Don't hesitate to go over the department, your institution has a responsibility to provide you with proper supervision.