So how close are you to a direct hit? and how intense is Dorian expected to be when she hits. Everything I've read about surviving hurricanes for a docked/moored boat is about being able to outlast the storm. Tie on multiple lines, with plenty of slack to allow the boat to move. Allow the boat to ride up/down as the tide/surge comes in/out.. Remove anything that produces windage (sails, sail covers, roller furling jibs, dodgers, etc.). Expect that of the 10 lines you tie to your boat to hold her in place, 9 will part before the storm is over. As long as your lines last longer than the storm (last line doesn't chafe through or break) you good to go. In reading stories from Hugo and Ike in Texas, that is how people managed to get their boats through epic storms. Look also at how your neighbors are tied off. Often its not your boat but other boats or docks which break free and cause havoc in a marina.
Good luck, I'll add an extra prayer for everyone in Dorian's path tonight.