wilwood problems

And you have the frontmost reservoir plumbed to the front brakes right? Duh that's what it says,lol.

Well then my next move would be to prove the compensating port is working, and then;
determine if this is a hydraulic issue or a mechanical, to wit; I would C-clamp the front caliper pistons into their bores. If you have more than 1 piston per caliper, then I would push all the pistons back into their bores and fit a solid metal bar between them then pump the brake pedal to clamp it in there. And repeat on the other side; then pedal test.
If still spongy there are only three possibilities; 1) air , or 2) soft hoses, or 3) caliper flex. OK a 4th possibility is cross-talk between the front and rear systems inside the combination valve; but since it didn't happen when the other end was capped, I doubt this.
But if still mega travel, then re-check your compensating port is open.
But if now hard,with nearly no travel; then you have a mechanical issue. Since with multiple pumps in the video, I did not see the pedal come up any higher,I'm doubting mechanical, unless the compensating port ain't working.

When everything is working right, you will have a high hard pedal, using no more than perhaps half the total available pedal-travel, more likely a third. And the reason is so the back-up safety system has room to operate.