I agree with Doc, you may want to consider rounding up a minimal amount and I don't think resale has much to do with it. The only point would be if you're close to 150 anyway, buy the 150. However, since you state you are looking at about half of the points needed for a 2 BR and assuming you'd avoid the Sat night, that would be around 100 points (200 every other year). With the extra 6 points per year and the flexibility to get a smaller room at times and maybe only stay the 5 nights some years you could enjoy some of the surrounding areas like Savannah or Charleston, you likely don't need more extra than that.
Though everyone on this board knows I'm not a big proponent of using DVC to exchange, HH is the perfect area for that purpose due to the very low off season points costs as low as 55 points for a studio week. If you have any plans to use DVC for exchanging, you might want to consider an extra few points to accomodate that, maybe another 20 or so beyond what I discussed above. Owning HH and OKW are the best IF you are exchanging.
One other consideration, blasphemy I know, is to consider a non DVC timeshare on HH. You can get a Marriott 2 BR for about the cost of the 100 points and have it every year. You can rent or exchange the years you don't need and even have a bonus week that you could use off season. The benefits of the bonus week depend on your schedule and flexibiltiy but can be very good if you can travel off season or even fringe season. Of course you could look at an Oceanfront resort but it would be much more expensive. Owning Marriott complements DVC nicely as several on this board can attest. Good luck.
Dean