I believe the xp reduction only works as far as the crafting cost is concerned (1/25 of the gp cost, right?), it wouldn't work for any spells cast in the process with an xp cost as far as I'm concerned...
A444: You technically use LA buyback as soon as you have the template, right?
So I'd say you'd be ECL 17 as far as LA buyback is concerned (so 16K in buyback)...
But what if you are an Artificer? You don't have to actually cast Wish or Miracle, you just need... I believe it's a DC 37 Use Magic Device check to emulate it, which is no problem whatsoever considering take 10, and the possibility of a first level infusion granting 2 + half CL circumstance. Hell, you probably don't even need the infusion. I think Warlocks can do the same, I dunno.
As for buyback, it really only accounts for inherited templates. It doesn't explain at all what you do if you get an acquired LA 1 template at a higher level aside from that (x - 1) * 1k thing. Which if that is what it is, then the sooner the better.