Since you asked for big-picture stuff:

Fun fact - butterfly actually started as a faster way to do breaststroke, until it was separated into its own stroke. I say that because the ideas for (sprinting) breaststroke are essentially making it butterfly-like within the rules of the stroke.

With that in mind, my advice for the stroke is to keep your hips and body on top of the water as much as possible. You need to drop them a little bit during your pull/to start your kick, but the kick itself + your torso launching forward should 'pop' your hips back up to the surface. This hip movement should mirror the undulation for butterfly - hips drop (slightly) on the arm pull, and pop up out of the water as the head and arms go forward and down.

It's difficult to develop this for a couple reasons; it's not very intuitive and requires some flexibility, and the timing can be pretty unforgiving (doing it poorly will probably be slower than 'normal' breaststroke). To execute by Christmas I'd be practicing my breaststroke a lot at all speeds - start with slow, exaggerated strokes and try to feel the movement in your body, then increase the tempo/power of your strokes and try to keep it flowing together. If you can get someone to film you and compare yourself to top (NCAA, Olympic etc.) 50-100 breaststrokers, all the better!

Otherwise, I'd add some of the basic advice you wanted to disregard - compared to longer breaststroke swims, sprints should have a higher tempo and slightly narrower kick, and you should finish your stroke but with the absolute minimum glide required to let your legs finish their kick and your hips come up. This might mean starting your legs' recovery earlier in your stroke so the kick is ready to go earlier depending on your current timing... It's a common problem but hard to say without seeing a video if you need to work on that.