If the books didn't help, then maybe your therapist is right, adoption may not be the root of your issues.
My advice, and frankly, you may be getting what you paid for, is get a new job. You are miserable there, and my guess is that sense of unfulfillment and missed dreams just festers and carries over into all your relationships.
Starting over at 44 won't be easy, but we aren't our granparents generation, we aren't dying at 60 anymore. You have plenty of time left!!! Go get that advanced degree, work at a college, whatever your dreams may be now! (I'm also a public school teacher, and the pay can't be that great!
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If you're angry at God, that must mean you believe in him. He can handle your anger. Maybe it's time you quit blaming God, your wife, your adoption, and take a good look at what exactly do you want and how can you get it. It's comforting to stew in our own anger, and feel like everyone is against us, and life isn't fair. I know. I've been there. I also realize I am coming off a bit harsh, but I wish someone would have told me to get a grip, and knocked me to my senses.
A few years ago I went and interviewed for several other jobs and came to the realization that the grass wasn't greener, and I've never been happier teaching. You may not come to the same conclusion, but the interviewing and researching was freeing to me.
Once I was happier at work, things got better elsewhere. If you don't hate what you're doing 50 hours a week (or more), it makes you a bit happier and relaxed in other areas.
Good luck. I truly hate you feel this way about your life. I've been there, and it does suck.