Indeed, the Caps function doesn't need a good position (unless you're Sean Wrona and use it for normal typing that is!). Mine is on Caps+Esc so I can hit it with one hand (but I rarely do).

With PKL Extend (SC001 = CapsLock). But it's entirely doable in pure AHK of course – although I don't recall the syntax for it. Might be:
CapsLock&Esc::CapsLock

The tilde isn't a Back but a Del (that is, delete forward). It's only there as a supplement to Caps+; for one-handed use and as such, not in frequent use. I found it neat for some browsing situations but I hardly use it now.

In PKL, I'd use a 'SC029 = }queue{' Extend mapping. In pure AHK I think it's just 'Caps&SC029::queue'?

Plateau's seem inevitable, only practice seems to get through them. I can't tell progress on a day to day basis anymore, it's only looking at small gains over the last 2-3 weeks that I can tell I am getting better.

As for "queue", I am a programmer and end up typing that more often than I would like, that and the word "true".  So even though it's doesn't feel nearly as natural as some other alternate fingerings, I do use my pointer finger and middle finger to type it. It feels cramped but I prefer it to the same finger motion.

I lied, or improved. But my typing speed is back up to 60 wpm, using the TECK.

I have this problem with the ergonomic split, and I noticed it the last time I used a curved keyboard. I feel like the curve is too much. That makes sense since my last keyboard was a straight keyboard. But here's the funny thing. I chose a split keyboard this time because I feel like it should be curved when I type on the straight keyboard. That is, on a straight keyboard my hands are too curved, but on a curved keyboard, my hands are too straight. I hope I get used to this keyboard.

I'm up to 75 wpm now. My goal is 100 wpm.

Broke 80 wpm. ^^

How do you set instant death mode? I don't see that anywhere.

I think it's a good idea. Speed is so critically attached to a low error rate and that's a good way to emphasize it.

I'm up to 80 wpm with 100% accuracy.

Instant Deathmode has been paying off for me. As I said before, the score is skewed, because it doesn't show all my failures. But it paints a clearer picture. Imagine that you can see all my scores, with the ups and depressing downs. Sometimes, it even looks like I'm regressing. But in all the times I scored lower, I likely made a typo. So, if you view this same progress with only the 100% accuracy points, it looks like points with long stretches inbetween, but each point is a little higher than the previous. ^^

after a while.my Colemak typing speed is  about 60 wpm,accuracy is 98%

On hard to type words, my humble opinion as a layout tweaker (I don't use Colemak, but a custom made version of the AdNW layout, that I sometimes change a bit to "perfect" it ):
* every layout will have words that are hard to type. Good layouts have *less* hard words; bad layouts have lots of hard words.
* once a layout is good enough, optimizing for one thing (say: a Colemak typists wants the letter H on the home row) will give problems elsewhere
* every layout will also have words that are easy to type, that you can use to brag. Classical example: you can type TYPEWRITER on the Qwerty top row

tl;dr - Live with it  :-)