You should have a conversation with your counselor about the math class. Ask if s/he plans to check the “highest rigor” box on the counselor evaluation portion of the common app and if not, if taking honors math would change that. The merit awards are going to go to the applicants who have higher GPA’s with the highest rigor first.
In our experience receiving the top non-competitive merit awards for private schools was typically $25-30K (tended to be about half tuition). Then they had a few competitive awards for full tuition, etc but you can’t plan to receive an invitation to compete in the final rounds of those.