For those people picking on stroke rate, I gotta say that I don't care about that. as long as you are comfortable changing stroke rates and can maintain whatever stroke rate you want for the distance, that's fine.
I'm more interested in the mechanics of that kick. it looks like even though you're doing a 2 beat kick, you're still overkicking. For distance swimming at lower intensities, you're generally better served by making the kick as minimal as you can. That doesn't mean don't kick, there's a balance there, but right now youre doing a massive kick with each pull. that just adds drag and doesn't really gain you much, especially with how inflexible your ankles appear to be. For distance swimming, I go for a feeling as if I'm just kicking from my ankles. In reality a lot more than that will move, but the idea is to keep the legs in line with your torso and just get a little bit of lift and rotation from your feet.
for the scissor kick, you're overrotating on the breath. so that's part of it.
If you're having difficulty with the 6 beat kick, a good one is to do a drill called 6 kick switch (there are other names too). kick on your side (bottom arm outstretched, top one at your side, for about 6 kicks (it can be more, doesn't really matter), then without breaking the kick rhythm, do one stroke (half a stroke cycle) then repeat on the other side. You can do it with a snorkel and fins to make it easier.
do a couple of lengths like that, then a couple of lengths where you take 3 strokes, then 5 strokes. just concentrate on keeping the legs in rhythm, don't worry about arms.
Swimming Workout of the Day: Favourite Swim Sets: 2020 National Masters Champion - M50-54 - 50m Butterfly