[wellboy]

You have 2 options.

1. You rewrite the code. You said you would hate that, so not an option 2. You develop on top of the spaghetti code. You said you would hate that.

So, no matter how, you would hate working at this job.

That's why the only option left for you is really telling your boss how things are and that you can't see yourself working on this project.

You'll probably receive an offer with a 50% salary increase, so you can take that, but you should have a new job lined up already at another companyy.