I love the video, it fascinating to see how you try different estim electrodes and TENS setting, keep it up, you WILL have and orgasm and after you do they will come easier and better as you learn what works best for you!
HFO with an ordinary TENS unit can be difficult. It just doesn't give the required waveforms that provide the best sensations. I have been trying to do the same with various different TENS machines and never got close.
I’ve done this a lot, focus on the underside of the head with a steady pulse and you will cum. I have a couple of videos of me cumming hands free on my page.