I’ll let the lawyers & landlords give opinions on how to break a lease, but you might decide that paying an extra month’s rent isn’t so bad. Especially if your closing slips past Dec 15ish.

I think you’d be doing really well if you manage to close around the 15th and be completely moved in by Dec 31. It took us 3 weeks and a bunch of help from our friends to do some small upgrades (new furnace, new bathroom fans, hot tub wiring, some drywall work), paint the house, move everything in, and clean out the old place. We made good time, but we really needed another week. So, while your specifics may be different, think through exactly what you want done before you move your shit in, and allow one more week than you think you need.