It’s a tough one! The best lead singers / front people are those who are constantly striving to get better.

I’d say your points could deffo be classed as constructive and if the singer can’t handle that sort of critique then the music business might not be for them.

We have a policy in our band that all criticism like this should be done openly (and frequently) with the whole group.

In the end of the day you’re only trying to make the group better!