Well, welcome to the "airline" world--full of wannabe hardazzes.
I totally believe your story about the FSDO. The flight school I went to had everyone pass the CFI, until one new guy at the FSDO showed up and started failing everybody, because they didn't teach THE WAY He Wanted. Remember the saying "I'm here from the FAA, and I'm here to help"?. Ever heard "Mike Colgan is a friend of this [FSDO] office?" Our school stopped using the FSDO which was on the field and the owner took it up the chain of command. With that said, you're going to have to learn to be an actor in this field. Hold your convictions, but play the game. "Own your mistakes" is sometimes code word for "eat crow so I, the examiner/interviewer am vindicated in my narrow little view". Esp. in the airlines, which has a fair amt. of instructors who never were a CFI, have no clue what the FOI's are and don't care AND who still think their job is to "wash you out", rather than instruct.
Regionals are going to hire you with 4 busts, because they have no choice and they have training depts. to do their own evaluating. If you get thru training and do well, and keep passing checkrides, those 4 busts will dim on your resume. Don't let someone on this board with their own twisted motives decide your career. Also beware the "old school" guys, There's a lot to be learned from them, but you have to separate good advice from jaded or entrenched opinion. KEEP AT IT and bust your butt! You will make it! P.S. you gotta have thick skin; just wait 'till you get on line and have to do a month of 4 days with "a captain on everyone else's no fly list".