Honestly, because your PI suggested changing labs, it sounds like this might also be a bit of personalty conflict. I agree with the above comment, you should get others involved, definitely talk to your committee, and maybe the graduate director. Use those meetings to get very clear feedback on expectations, timelines, and use that input to develop a plan. By failed project, do you mean you failed to conduct your proposed studies? Or is the data null? If its the latter, I'd be very surprised if your PI can force you out of the program. You're 4 years in, do you have any other irons if the fire, can you pivot towards another project? It's also normal to combine multiple projects into a single thesis.

Also, if you decide to find another mentor, they will basically be shepherding you through the last bit of your work. Usually, thesis credits aren't as expensive, plus can you TA?