Single speed chain alignment
At $40US for a Profile internal Euro BB I'm struggling to see what you're hoping to gain here. One major thing you'll lose is the narrow Q of your current cranks, which most would consider negative.

But,


Normal BMX 1/8" chains like a 410 or 410H will work on a narrow-wide ring. I haven't put a halflink chain on one but I don't imagine there being a problem. Note that the NW profile might as well not be there in a singlespeed drivetrain and is basically money wasted, but they do work.
142x12 is essentially the thru-axle adaptation of a 135 QR rear end. The bigger number is due to how the ends of a 142 hub recess into the frame. So for the most part, 142 and 135 bikes have the same chainline considerations and use the same front end configurations. Presuming you have some kind of SS freehub, you should be able to use spacers to get your chainline good, but it will be different from where you've had it. Most 135 SS freehubs can go to about a 55mm chainline at the outside. Since Superboost cnailine is 56 that probably means you have impunity between getting a 142, Boost, or Superboost crank were you to do this.