One of the issues you didn’t explore is why a preacher’s son would become a chronic liar. I’ve seen it any number of times. One possibility is that you didn’t feel you could live up to the standards that were set by your parents. Not feeling you could be the best, you went 180 degrees and became the best at being the worst — and you did it mostly secretly so you could maintain their high regard but protect your self-esteem by identifying yourself as a successful liar.
The Marines apparently gave you a “second chance” and, to your credit, you took it. But once you went back into familiar surroundings (and without the high structure of the military) you slipped right back into your “old skin.”
In your letter, you mention that you tried counseling only once and with a religious counselor. I suspect that a counselor with those credentials is too similar to your parents. I also think that you probably lied to the counselor.
I strongly urge you to seek out counseling from a licensed psychologist who does not identify as a religious counselor. Send a copy of the letter your wrote to PsychCentral plus this response to the therapist before your first session. That will at least lay out the problem honestly and will jump start your treatment.
Your letter was a good first step but unless you follow up, it will go nowhere. Do make an appointment with an experienced and licensed therapist and get down to the real issues. You are still young. You can still change and make a better life for yourself.
I wish you well.