So the way the kite changes camber depends on 2 things the ratio of the mixer and the positions of the bridles or more particularly the position of bridles between A and Z. So to get a linear relationship, that is to say the camber changes not at all or "the least", you need the mixer ratio to match the bridle positions. So for 1 pulley 2:1 mixer B would need to be exactly in the middle of A and Z. For a 2 pulley 4:2:1 mixer B would need to be at 1/4 and C 1/2 between A and Z. For a 2 pulley 3:2:1 jakomixer B would need to be at 1/3 and C 2/3. So the principal for changing any of these is the camber increases or decreases. That is if we take the 1 pulley mixer at 2:1 and we place B forward of 1/2 the camber will decrease because the pull on B will increase beyond it's flat or linear ratio as the mixer is pulled more. If we place B past 1/2 then the opposite happens and so B is pulled less or Z could be looked to be pulled more.
Now there is a third effect that is with a camber increasing setup you can have a period where solely B or and C is pulled and so camber decreases and then reverses to increase. With this you have good stability depowered but then also good performance powered. Simple trick but worth exploiting if you can.
Now enter your kite. You have so many bridle attachment positions you can practically match it to any mixer however you want. The question is what do you desire and what would work best? So the advantage to a single pulley is you get a lot of travel for little bar, but the disadvantage is especially for a single skin you may not have enough bridle support with that. That is to say you are going to have a large portion of the kite supported at a single level. Fine if like on a paraglider everything is basically fixed and you can set all the levels to be right, but on a mixer where things move and change then maybe not the best. You will end up with a weird stepping effect on the airfoil. If you look at the Peak 3 you will see it has a sole row for B and C and Z, this avoids the stepping. Now you have a lot of bridle points and using 2 pulleys you are still going to have this effect but it is better than 1 pulley, you could go 3 or 4 pulleys but I don't think that is necessary. Were you to fix say row 1-4 as A that leaves you much less rows to deal with, now you have 2-3 rows per pulley, not ideal but I think it will work.
As to the play of camber on a single skin I think maybe you are over worrying this point. What is most important is you HAVE TO HAVE bridles to support the wing or it will collapse, which is what can be seen with yours in the vids... You can get away with only supporting part of the cord though. If we look at the peak 2 and 3 using my eyes and the diagram which neither may be accurate
we see that A supports about the first 1/4 or the cord. So if we look at your kite
that would be about row 1-3 INCLUDING those tip bridles. Me personally I might just fix all those tip bridles onto A. Now an interesting effect when you support the front of the cord and then completely unsupport the rest it will flap. Flapping increases drag. Increased drag means to kite sits back having more AOA and too has a much harder time flying forward especially if the wind changes. The net effect is you get very stable depower as seen on the peaks. So the important thing for stability I think is how much of the cord you fix to A or rows 1-3 or 1-4 and how much AOA you give those new A bridles, or what shape you set them to.
Now it has to be added I do not know what flysurfer is doing with B on the peak, it could still retain tension depowered. Which would change things a little. But you can likely take the same approach if need by just altering the mixer.
In addition there is some difference you will get with the different mixers that is unavoidable. To get a similar approach to camber change they will be supporting slightly different parts of the cord. This will come with benefits and negatives. It could be that the most evenly spread support is the best so the standard 4:2:1 where as the jackomixer leaning to more rear support is not as good... or maybe the reverse, as I have not tried any of this.
Good luck, but yes you need to fix that collapsing. Get the A bridle right and maybe it needs some of the centerish cord fix on B.
Oh and to add looking at the row positions of your kite in the diagram, they do not look accurate. You will have to calculate this on the kite. Use a measuring tape or fold the kite to estimate things. Make a plan, I think follow what the peak does, and execute it.
And lastly as I keep adding things
. I would love to help you person if I could( obviously can't) and I think it's a really cool project and how great if with relatively little change it works well! I wonder if Ozone or someone would release a kit to do similar.