What does your contract say? I doubt they tied themselves legally to a completion date (even good contractors rarely do that as so much can happen).

The time to stop by and see progress is while workers are there and as for the key lock situation that should have been you getting the lock and taking the cost off the bill or getting a locksmith to rekey the lock . I have no idea what was being done so maybe some pictures of the house before and now and also a description of what you planned .I know it is stressful when bad things happen but we really can't help and for sure not without a lot more info.

Three words: get a lawyer. Full stop. All of what you describe is totally unacceptable. Do not pay another cent or allow any more "work" to occur until you have spoken to a lawyer.

Wow, you were much too accommodating to be left hanging for 6 months more! At week 7 I would have stopped the ferris wheel and changed my locks. Read your contract and get professional or legal guidance on your next steps. Tell them your working on your invoice too and that you'll let them know what is owed to you as well - works both ways. Good luck!

I don't know how you managed to allow them to keep you out for 8 months from entering your own property to see whats going on. You're lucky they didn't move someone in there and rent it the place out. Something similar happened here in a beachfront co-op, someone moved in and here comes Covid and they can't get the guy out. For 2 Years he has been enjoying the beachfront co-op.

As RappArchitecture suggested, get a lawyer because you don't want this person back, collect all the evidence of incompleted work or "botched-up" work, get a few estimates of what will cost to make you whole, and most likely you will need to pursue this with legal action.

Agree with all the comments about getting a lawyer. This sounds like a terrible mess.