It's the Christmas edition of The Real Book
Not really theory-focused, but if you can read lead sheet, I'd recommend a real/fake Christmas Book like this.
I'm a semi-jazz beginner too, and I've had the most fun playing through xmas songs from the fake book. After a while, I find myself picking up on adding maj7s, 9ths, or just trying to fit bass-lines wherever I can and it comes off as quite jazzy. Not official jazz theory, but I find learning theory after having experience is the way to go, otherwise the theory we learn has no base.
I don’t think I’ve found anything that’s good, with all of the books I’ve seen being incredibly simplistic. Like...melody and open chords on the downbeat of each measure levels of simple. I usually hash out my own arrangements using the Real Christmas Book because it uses much more interesting harmonies (though there are some stray wrong chords mixed in that you’ll want to mark out).
I know it's a little early, but it can take time to work up some of these songs for the Holidays. If you're looking for a solid set of lead sheets, check out The Real Christmas Book.
You could get some ideas from the German band at Epcot:
https://www.youtube.com/watch?v=CDZ7Fn8a1_w
It might take some clever googling, but there should be a lot of footage for ideas.
Also, there is an official Christmas realbook. If you understand how to play a polka, you should have no problem faking any of the tunes as a polka. Also, not sure about the Kindle version, but if you acquired a PDF of the book, it would make using it so much more convenient...I think iGigBook has catalogued the tunes.
Christmas Real Book 1 (warning NSFW YOU MAY FAIL NNN) here
You might look through an old Christmas music mega thread.
I personally love the Real Christmas Book if you know (or can learn) how to use leadsheets.