OP, I left my ex in secret. I found a place for DC and I to live, organised some new furniture (well, second hand, some of it free from a few family members in the know), and planned everything in secret.
The day we left, we got up as sone as he'd gone to work and packed everything into bin bags and into a van I hired, doing several runs.
He didn't know until he came home from work that day and found us gone.
I do regret leaving my books, but I ran out of time, and he wouldn't entertain the idea of me coming back to collect them, unless I was coming back for good. No chance of that, he was abusive.
The last few weeks, from the point of securing the house to leaving, were the hardest. It actually included a family holiday, we couldn't leave before then, or I would have taken the holiday and left him out of it, as the booking was all in my name. He didn't actually know the exact location, only the town.
Since then, the DC have flopurished. We have had to deal with MH issues caused by living with ex, but life is so, so much better, and peaceful.
I'm currently in the process of losing weight that built up due to comfort eating (I've worked out the triggers and am forming new habits), and am doing work on strengthening my boundaries, and maybe next year I might begin dating again.
You can do this, living a "double life" until you leave. It's hard, but doable. Just keep that goal in front of you. Visualise how life will be, plan what you want to do on that first evening on your own. Movies, favourite foods?
Oh, and once you have signed on the dotted line for the house, get onto your preferred broadband/tv provider to get appoitments set up, because they always take time in my area. I called to fix up installation, and it was still 3 weeks before they had an appointment. We were able to watch DVDs through DS's XBox, so we did that and played boardgames in the evenings. It was actually lovely.