How about some very-well-read, but totally inexperienced advice?
1/2 cup is a little on the low side. 3/4 cup for a 5 gallon batch is typical. HOWEVER, you already have a higher than usual gravity reading. I would bet you could've bottled without any priming sugar and had decent carbonation within a couple of months. If you've got some fizz after the first week though, then you are definitely on the right track because most people report the same thing. Obviously, it's going to get better over time. So I think you're just fine and probably smart to use a little less priming sugar given the higher gravity at the time of bottling.