>be me, looking for new jobs
>boss doesn't know
>he likes me a lot as a person, but job is shit, pay is shit, no chance of raise or upward mobility
>this is the entertainment industry so all the above is normal, and an opportunity hundreds of people fight for
What would the pros and cons be of telling him I'm looking for new jobs? The only pros I can think of are not hurting his feelings and ensuring he'll be a good reference later
You have nothing to gain from telling him, and everything to lose.
Never let your employer know until you've been hired somewhere else and signed a contract.