I know this is not the advice you want to read, but using your points for a cruise is not a good use of your points, especially if you have to borrow.
There are many reasons not to do this....
Rent, pay cash - Its cheaper.
No OBC
If you cancel, points do not return to UY.
Paying cash, you can get a full refund...within rules.
If you use a service, like the R/T board sponsor, you'll have money left over for excursions, gratuities, transportation...etc.