Yes, you can bring boat over, pay for slip, take ferry back.
No issues leaving it empty, plenty of people do it.
Just make sure you have a reservation so you have a slip.
Looking at your boat I am going to assume you cruise about 30mph?
At that speed, I woudl figure a hour from seaford.
Adjust accordingly.
If you leave you boat, please leave it unlocked and let us know where the alcohol is stored!
Thanks!