I've got a new bike trainer which has made fitting my bike way easier. Unfortunately, this also results in a lot of uncomfortable riding, and I'm kind of at a loss with how to progress. What I have done:

1. Raise saddle to 28.5" from the crank spindle using inseam measurement.
2. Lowered saddle tilt angle to 3 degrees.

Problems:

1. I constantly feel like I'm going to slide forward. I am having to put a lot of pressure on the bars. I've read this guide which was a nice explanation of everything. But there is absolutely no way I can do this:
2. Pretty much guaranteed as soon as I take my hands off the bars, I will fall forward unless I am sitting straight up.
3. KOPS also seems pretty much impossible for me. I have my saddle slammed all the way forward. I'm not sure if I'm just like sitting on the saddle wrong or something, but even with the saddle all the way forward, my knee is barely over the pedal spindle.
4. My left knee has also started having pain on the superior and anterior portion since messing with the saddle. My ischial tuberosities also hurt like crazy even with pads.

What I am thinking of doing:

1. Going from my 25mm setback seatpost to a 0 setback seatpost.
   1. Possibly going from a 100mm stem to a 90mm stem. Or raising the handlebars up to the top of the headset.
2. Lowering my saddle. Uploading a video currently, but it looks like it might be a bit too high as my foot appears to be plantarflexed at the bottom of the stroke for maximum reach. But I think this might also be due to not feeling stable on the saddle?
3. Going back up to >8 degrees of angle tilt? From everything I've read, this should be absolutely destroying my crotch, but it's so much more comfortable.
4. Possibly looking at a different saddle.

Video:
0:00 - 0:42: warming up
0:42 - 1:12: 10-15 minutes in
1:12 - end: cadence ramp up
https://vimeo.com/412095292