Help!!! How do I tell my boyfriend he is not funny and can never make it as a comedian

Morning Emeh .Here is my problem and I hope you can share with your readers.
I've been dating my boyfriend for 8 years since we were in the university. We read Geography and after going for Youth service, I got a job as a Geography teacher in a secondary school but my boyfriend decided to be a comedian.This was because he was an MC at his friend's birthday party and made a few people laugh. Since then, he has been deceiving himself that he is funny and will be the greatest comedian in Africa, not just Nigeria. It's been 3 years since he started this comedy thing and I've watched him get booed, thrown pure water and insulted.The bad thing is they are all free and house parties or school parties .
The truth is he is not funny, he can't even laugh to save his life and when I stylishly tell him to look for a job he starts telling me of top comedians in Nigeria who started from the bottom and made it. He said he knows this is his calling. I think it's my fault because even when he tells me his boring jokes, i laugh by force.
I've never seen any top comedian who has been booed as many times as he has. So I know he cannot make it as a comedian. His friends laugh behind his back.
Now I'm 29 and he is 32. He feeds off me and keeps saying how he will buy me diamonds and houses when he makes it. Is it when i'm 50? I also have a banker on my case who is pressuring me to date him .
Please I want to give my boyfriend an ultimatum to get real or I leave him. Am I wrong? And how do I tell him his jokes are not funny without hurting him? Thank you all in advance 
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