That’s going to be a recurring theme: quit and lose the contract but save your time/energy, or follow through and grow resentment because you’re getting underpaid doing something you originally didn’t agree to do. Scope creep kills projects, and this is what makes software development so difficult to estimate.

You did get incredibly valuable life experience from this though, and hopefully you’ll be able to stop it in its tracks earlier, but never be afraid to walk away from a job.