Do I have enough visitors to cover the cost of doing this (currently 500/month)?
I have two hands, is it enough to earn a living? Well, it depends on what and where I am doing a lot.
Visitors do not magically make money appear. Advertisement is part of the process and it depends on a lot of things how well advertisement works in specific niche and how much money it makes on average per visit.
What I am restricted from doing if I do go with WordPress.org?
You can do absolutely anything, as long as it complies with Terms of Service of your hosting provider, laws of hosting provider’s country, and laws of your country.
If I make the decision to go one way or the other, how difficult is that decision to reverse?
The basic import/export of posts is not complicated, but if you use theme/plugins which aren’t available on WordPress com obviously you would lose those parts going back to it.