Nicely done.

So.... I'd back off on the flute in the sections where the singer is singing. You should almost never have anything competing with a singer. It's very distracting.
Regarding the singer getting weak on the higher notes.... yep.... I have had to deal with that too. Of course you want to go for the high notes because they just sound better. Sometimes switching to falsetto helps. I'd suggest playing around with the parameters of the voice. Power, as well as gender can keep the voice stronger and using automation to adjust those parameters just where they are needed can be very helpful. TBH, I'm still trying to figure out how to do a few things and automation of certain areas is one of them. I know it's possible.

You can find my music at:
www.herbhartley.com
Add nothing that adds nothing to the music.
You can make excuses or you can make progress but not both.

The magic you are looking for is in the work you are avoiding.