Advisor doesn't let me graduate and prevents me from working
Let me suggest a couple of things. You may not be happy with the suggestions, I realize, but it is a &quot;safety first&quot; recommendation.
I suggest that you agree to 4th project and that you commit to it. But I suggest that you don't leave it open to a follow on 5th, 6th, etc. Try to come to a firm agreement that this next big thing will be the last he asks and that you will then be able to move on with good recommendations. Hard to get a guarantee on the last part, but it is what you seek.
There are two major reasons I suggest this.
First is that it is now a terrible time to be graduating. Higher education is in flux because of the pandemic and it will take another year for it to settle out. Hopefully it will by then, but a &quot;novel virus&quot; presents an unknown future.
Second is that fighting with your advisor is not a recipe for academic success. Going to the chair with a complaint might poison the relationship and leave you without a future path. I don't know if the advisor is abusing you or just thinks that with a final push you can open more doors in the future. Doing more than the average is actually expected, though not always achieved.
If your funding is in place to continue and you want to maximize your future, consider following his advice.
And if you are actually depressed, go see a professional. The university probably has a counseling office for such things. What you are feeling is pretty natural, actually, but you may need advice about how to get through it.