I think he should find another job Being a singer it's definitely not for him.

I have anxiety issues, so I know how hard it is. Plus the pressure of stardom must be enormous.

But, he has a job to do. One that he chose of his own volition, and there are consequences to him not attending performances. He needs to either work out a way to sort out his problems, or choose another career. Doing it once is bad enough, but several times is unacceptable.