It's hard to know what's really going on here. What was the scope of the project? If you pulled the permit as a homeowner...you've already tried to sidestep the system and now have a problem. If you hired a contractor to turn a large renovation and he isn't a GC, that was the beginning of your problem. What was the initial scope of work and what was the cost? Investors....all of us...tend to be too cheap on rehab and then, especially unseasoned investors....end up with huge problems. I knew an investor in NY who did a huge rehab without the proper permits....the town waited until he was done and made him tear it all down and start over! Can you imagine?
Putting two different contractors on the job like this is a mistake...one will interfere with the other and the finger pointing starts. You can't really rewrite the contract. Taking him to court is a waste of time for both of you. Either sit him down and see EXACTLY what the problem is and what it will take to finish up his portion....write it up and sign off on it. If you can't work it out with him, get him to sign off on a full waiver and release, return the architectual drawings/plans whatever you are referencing in the post....and part ways. You are best to clear out the other contractor or get him to finish before bringing in another guy.
We recently got brought in to finish up a project for a flipper in atlanta. The project wasn't overbid at all....the contractor had plenty of money to get it done. The project was 6 months behind....the investor hired a relatively inexperienced contractor who spoke fluent spanish and ended up using whatever scab labor he could find off the street. My group was brought in by the buyers to finish the place up so it could close. It almost came down to a fist fight with the other contractor. All kinds of issues...electrical outlets ungrounded, plumbing issues, flooring issues, a deck that was built wrong, a new master bath that didn't make any sense with a shower door hung wrong, a shower pan that had been nailed through, roof repairs made with 3/8" plywood, roof leak "fixed" by caulking the shingles.....new vent boot that wasn't nailed or seal, bath fan this venting into the ceiling....an unreal list. The seller made most of it right but it was a ton of headache for everyone involved. But the investor was new to the business and went with a personal referal that turned out to be a nightmare.
For this guy, the budget was correct for the scope of work...he just had the wrong guy on the job. The permit was pulled by another GC but the other guy was the one running the job. If your contractor shows up in a honda civic to do your work.....you might just have a problem and that was literally the case here. Try to video the project at each draw so you can see the progression....the bulk of contractors work on draws so those saying "no money upfront" have no idea. New construction is pretty straight forward...if it's renovation on an older property budget in 10% to 20% for unknowns. We're on a project right now that had tons of termite damage and subfloor issues which we had no way of knowing or budgeting for prior to starting the work. These kinds of things are unknowns until you start....and always put as much as you can into the contract from go. Luck with it!