I'm sorry to hear you had such a ruff time. That's not cool about your stepmom, and your mom not supporting you. It must have been hard to stand up to your SM, PSTD aside, sometimes people have to stop making excuses and start taking action to fix it.
I spent my holidays, fighting my MIL who decided to defend my Mom and sisters, and DH who defended his mom. I had to re-explain to people who it's none of their business, about what my FOO did to the kids last year, luckily I did save one picture(as I generally purge anything sucky), and how I will never be a human shield again. And everyone who is going to fight me, can scr@w themselves, DH included. I lost almost everything defending and protecting the kids, no way in h@ll am I'm going to go back to my FOO. I guess luckily, FIL stepped up and finally after starting the separation process, DH is starting to step up, going to T, etc.
Maybe now that the holidays are over, you can spend time with your dad but not with your SM.

Your Foo is lucky to have such a warm-hearted, mature person in there midst. Wishing you a happy, harmonious coming new year.