Maril -- This is the Northwestern University Thread, you may get even more responses if you post this question on the main MT board.
Those grades probabably would not get your S into Northwestern -- all students are admitted to Northwestern first academicall and then audition for the MT Certificate program once at the school... I think at the end of Freshman or Sophomore year.
As far as other schools go -- grades will carry a different weight in admissions decisions depending on the school. Some schools -- like University of Mighigan -- require all students to go through an academic screening before they are permitted to audition. Other schools weigh academics very little in the admissions decision. Other schools may weigh academics in the decision, but are at schools that are not as academically difficult to get into. Others do weigh them in the decision, but will allow all students who apply to the university to audition, and then see if they are competitive for admissions... I am sure that there are as many different policies and scenarios as there are schools!
I do not know the specifics of the programs you have listed above, sorry, but I am sure there are those who post on this board who do. You may also want to consider contacting the departments directly.
When you are putting together a list of schools it will be important to make sure you have at least one academic safety school that does not require an audition for admission to the theatre or MT program at which your S would be happy attending. This is the case for ALL students applying to MT college.... it is a highly competitive, and somewhat quirky process.
You may also want to look at 2-year conservatory programs such as AMDA or Circle in the Square. These programs are auditioned programs, but academics are not factored into the admission equation.
Best of Luck!