http://www.finaid.org/calculators/awardletteradvanced.phtml Here’s a calculator that might be helpful for you.
The merit money is locked in provided the student meets the requirements for keeping that scholarship. So ask. Sometimes the GPA requirement is pretty high. Also, ask what happens if the GPA drops, but later recovers. Will the scholarship be reinstated at that time, or is it lost forever.
How much can you continue to squeeze the family budget to pay for your share if/when your family contribution goes up or down in the future? Ask the financial aid offices about the specific formula they are using, so that you can make your own best guesstimate of the affordability of that place given possible changes in your family income.