Is taking 5 courses senior year second semester too little?

Again, talk to your guidance counselor - they will know enough to understand that you are or aren’t able to graduate.

After that, it depends on what your college wants - and what you put on your apps.

But many take less classes senior year including one of my kids.

You need to hit those two things - 1. HS graduation and 2. Ensuring you hit your college minimums

There’s not much more to this.