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.
Thanks Herb for your positive feedback and good advices

I now played again with the parameters and I noticed that adding tension and lessening breathiness would help in high notes... I guess that is quite voice specific thing and you have to learn how to handle the weaknesses of each of your singer - and I'm glad that they don't complain about it

Janne