Sorry OP, haven't RTFT but just wanted to comment on your original post.
I had been making a plan to leave DH...
You didn't imagine all the stresses that brought you to that point. It's a decision you wouldn't have made lightly. No doubt you minimised your feelings for as long as you could, but ended up knowing (as much as you CAN know, when riddled with self-doubt) that they were worth acting on.
I have been feeling really conflicted over everything because ... I was doubting myself if I should leave or not anyway. He's good to me in a lot of ways and we have a really nice life in a lot of ways.
But there must be plenty of ways he's NOT good to you, and plenty of ways you DON'T have a good life... see above! Also, feeling conflicted over everything is a natural consequence of having your life dictated by someone else. You comply as best you can, to minimise conflict, but a little voice refuses to be silenced...
I find it hard to make decisions or to know what I want at the best of times.
I'm guessing he belittles you for anything that goes against what he wants, so you've lost (or never acquired) confidence in your own judgement.
I can't ignore that I have had this voice in my head for a while now telling me to apply for jobs, make plans, etc.
See, I knew it! 😉
Keep listening to that voice! You will be so grateful, one day, that you did.
If you turn down this job, by the way, that little voice is not going to go away. I know you wish it would.
He was so angry when he found out about the job I'd got (understandably really as I'd done it behind his back), and I cried and apologised and ended up agreeing to not take the job.
There we go, I knew that's what he'd be doing. And so did you. That's why you had to go behind his back. I'm guessing that crying and apologising, and agreeing to what HE wants, has become second nature to you. 
Congratulations on finding your dream job! It's the first step to waking up out of this nightmare.