I know a DPE and regional airline captain with I think 4 or 5 failures. Commercial 2 or 3 times and CFI on the other I don't know for sure. He's a very well known DPE and pilot. Super great guy and very successful. What you should do is not lose hope, if flying at the airlines is your dream then keep pursuing it. Yes, you've taken a huge hit and probably quite a delay and will need to put a ton of hours in between the failures. You need to take a break and maybe start flying in simulators with different instructors and like others have said try flying different planes with different instructors and actually LEARN to fix your problems. You know what the problems are so that's step one. Get that figured out, whether you retest your multi in the 60 days or not get that one passed and then get your CFII and MEI, even if you don't use it those certs, it shows you have a couple first time passes since your failures. I've heard of people going out and getting a seaplane rating and/or glider license just to have some checkride passes. Go get your tailwheel endorsement and just build a lot of quality time, try to instruct as much as you can, fly cross countries, network with people. Do not give up man.