There could be up to a 20 minute wait for the bus, so if you're at the bus stop at 7:45, you should be on a bus to DHS by 8:05.
The bus may or may not stop at GF before going to DHS. If it does, you should be at DHS about 8:20.
You then have to walk a short distance to the boat dock, and wait up to 15 minutes for a boat, which puts you on the boat at 8:35.
15 minute boat ride to BC puts you at the resort at 8:55, and you still have to walk to the restaurant.
I would suggest being at the stop at 7:30. Then if you happen to get all the worst case scenarios as I detailed, you'll be arriving right at your reservation time. More likely, you'll get there 15-30 minutes early.
When DHS opens at 9, the first boat leaves DHS shortly after 8. If it looks like you'll be arriving at DHS much before that & you don't want to wait, tell the bus driver where you're going & they may be able to get a bus to take you over.