Your 100 sprint is 1:40? I think it could be faster, because the stroke looks smooth. From the video it does feels like the elbow position isn't high and you aren't catching the water

Why are you trying for a higher stroke rate?

Try to swim with clenched fists 25m + normal 25m. Try with bilateral breathing, so you get the feel of both arms.

. I have used Effortless swimming videos, but gave it up. It is too oversimplified and pull focused. Their success rates are very very variable. Some go from 2:00 to 1:45 some go from 2:00 to 1:30. That is sucha big big difference in long distance. It clearly leaves out a lot of stuff. It is like one of those online businesses focused on number game.