Well, got the head back on again, made sure to do the 70nm, 70nm, 90degree (with one of those stupid angle torque gauges, even) and the old boy won't start, still.
The first time, I did the valve clearances wrong. (I didn't realize that "valve fully open" meant the pushrod was all the way up and the rocker arm was all the way down upon the spring, so did it all backwards.) The rhythm of the engine was off, and it wouldn't start.
This time, I took the entire thing apart, got new head bolts, cleaned out the bold holes on the engine block, scrubbed more carbon off the piston heads, and then used the new bolts, in sequence, used the angle torque gauge to add the 90 degree turn, and still, the engine rhythm is slightly off (not as bad as before) and it won't start. Start pilot gets it going for a second before it goes back to trying and failing.
I'm uploading a youtube video of the engine sounds while starting to see if anyone can confirm it's the valve clearances, or if something else is wrong.
The thing about the valve clearances is that the Haynes manual is pretty vague - it says "make sure they're a firm fit, not loose, and not tight." But that's it. I don't really know what the hell that all means.
I should also mention that whomever was in there before put the head on a lathe because I can see faint marks. Head measures up fine, absolutely no warping whatsoever and no cracks. (I'm really wondering if I had to change the head at all or if the smoke wasn't just a loose injector, after all... but here I am anyway.)
Youtube Link
https://youtu.be/XYUGonq50YA