1. Definitely you will have time and if a school or hospital does not allow you to see a doctor because that dirty tooth is more important. Then don't go there for residency. Also, I believe it is illegal per the ADA, not our ADA, to prevent an employee from getting medical care. Accommodations must be provided.
2. Hours worked varies a lot during residency. While it is true that OMS programs are not bound by the 80 hour work week, most still try to hold to it. Very few resident unions out there. In my program residents can work 80+ hours but it is rare and not the norm. Sometimes you just have a lot of stuff to do.
3. See multiple other posts about this topic. There are many factors that weigh into a candidates matching.
4. Again, see other posts related to OS applications and "basic" criteria/requirements.
5. I have been out many years but I believe the one thing I wish I had known was how little dental school prepares you for OMS residency. I tell all my new residents to be available, be vocal, be honest, be excited and, never try something you have never seen or done. Always get help. Also, you get out of residency what you put into it. You will not be spoon-fed information, You need to be a good self learner.