Chris & Anewta,
You seem so determined to drive in the DR that it seems almost to be the purpose of the trip. I'm amazed that the horror stories mean nothing to you.
Otherwise, you've done a lot of research, judging by your number of posts.
Just because you can drive in Russia doesn't mean that you are ready for the DR. What will you do if the car is stolen or if you have an accident? You've indicated before that your Spanish is not especially good, and you don't (I suppose) have a network of friends to help you out of trouble.
It seems a nobrainer (a term not understood in the DR, by the way) to use other means of transportation, perhaps hiring a car and driver (if you don't like buses) for little more than the price of renting a car, but WITHOUT THE RISK AND HASSLE.
If I may take the liberty to go beyond this particular post, I even think that you should spend most of your vacation away from the all-inclusive and tourist areas. Yes, I suppose that you have a package that includes lodging, perhaps for less that what the airline ticket alone would have cost. That does not justify failure to take maximum advantage of the opportunity that you have to see the "real" DR.
Away from the tourist areas, small hotels are available for less than 500 pesos. You could take a bus to Santiago, for example, find a cheap hotel near the center, and do some serious exploring and "culture absorption" on foot. You could also hire a car and driver, if you wish, for side trips.
I would simply use a prepaid room in an AI for my first and last nights (near the airport) and forget it.