Nice video and nice pool !
I would work on balance. The feeling of accelerating/decelerating which you currently feel is certainly due to the increased drag produced by your not-so-perfect position in the water. Improving your hand recovery (elbow-driven) might also help you get your hips and legs more horizontal.
So if you get a better balance, you'll create less drag and you'll probably less have this feeling of accelerating/decelerating.
I would then work on your kick: use your leg, start your kick from the hips and try to lengthen your ankles (this also produces drag). And then, building on your improved balance, do some fine tuning to optimize your kick. I would aim at making less bubbles.