I've yet to do any serious speedruns on MGR mostly because it requires you to do the polearm jumps well and I too have been wondering whether framerates are also important to perform these.
Play claw, and look at the sky or ground if you have framerate issues. Slash and then blade mode cancel when done.
You are performing the inputs too early. You'll notice that in your example, Raiden stalls midair after pressing ripper mode for nearly a third of a second. Wait until the first swing is completely over, and you should see (slow but) fluid movement from when you perform the input.
Apart from what everyone else has said, I would just try jumping off into the right corner and doing 5 light attacks at the top of the polearm bounce. That's been the most consistent method for me in the runs I've done.
idk if this is an actual tip but after the 5 slashes for height i spam jump and pray to hit a ledge
