LLTs and defenders are REALLY powerful when you have over 9000 of them. What should I have done here? Daywalker had more scorchers than me and a ton of porc.

Ok, after watching:
RADAR! DayWalker countered every single of your raiding attempts by having his own scorchers around! You did do well by making him chase you, giving your scorchers an advantage from kiting, you pretty much contained him because of your constant imminent scorcher threat. The moment you relieved the pressure (by taking an unfavorable engagement and losing scorchers), he was free to raid you and immediately did so. Lacking proper radar coverage, you couldn't prevent his forces from rolling in and cleaning your expansion. Even 3 scorchers would've made quite a difference (Lancester...).

You weren't actually outecoed by much throughout the game, in fact it was pretty even. When you resigned, your army values were about equal!

I sort of liked your airplay, but you kept taking attrition from losing your phenix, while his scorchers usually survived the napalm (although you did keep his numbers and attacks down by doing so). If you had instead killed his windlines with your first few phenix, his energy economy would've been screwed hard!

Overall, DayWalker used more money for ground forces in the second half of the game than you did, which gave him an easier time expanding to the middle (and securing it with some lighter porc). When you saw the vandals you should've kept up radar coverage as far as possible, to see where they are going and where you're free to bomb (would've been totallly different vs jethros). Basically, it went downhill for you because of you taking attrition with your air.

The frustration when 5 shadows left his lab at 5 hp was apparent (and produced an immediate resign), but the game was far from over imo.