The thing I'd most like to know from this match is why my first Impaler never tried to kill the closest Stinger. You can clearly see on the replay that I issued a Set Target command on the Stinger's image, but the Impaler took two shots at other things instead even though at least the second shot was clearly in range of its designated target. General advice on controlling Impalers is also welcome.

Anyway, Lessons Learned:
1) I've lost two important practices from my earlier play: routinely using the "select idle worker" command to check for them, and keeping the raiders with my army separately hotkeyed even if they're mingled with heavier units.
2) The mere fact that my first combat unit was a Fencer, and Riposter's scout saw nothing else, was enough to get RiposteR to emergency build a Halberd! This Halberd never actually encountered a Fencer, so my bluff there made things easier on my initial raiding Scorcher pair when they fought Darts.
3) Scorchers maul Darts pretty badly in a head-to-head pass. They're tough enough to mostly survive the initial volley, the Darts can't turn away in time, and the Scorchers each kill multiple Darts before the next salvo.
4) Given that I invested in both a second Fencer and a factory guard Lotus, the two Fencers should have advanced as soon as the Lotus was done if not sooner. At 2:45, RiposteR had an army of one Halberd, one very damaged Dart and an out-of position Commander, and no static defense. My army was two Fencers and three Scorchers (one very damaged). I could've been sitting on RiposteR's factory by about 3:15, by which time RiposteR had two more darts, and I don't think RiposteR could have done much about it.
5) I'm not appropriately balancing my economy when reclaiming during the midgame. It's directly competing for build power with pregridding with generators, and that means I don't have the energy or build power to use the reclaim. Probably, the mere fact that there is reclaim on the map should cause me to alt-build a constructor before issuing the reclaim order, or I should automatically build a couple of solars with my reclaiming worker before the reclaim command.
6) My initial fencer move-out should advance to contact, not pause to regroup every so often. I left too much time to react after their dots entered enemy radar.
7) I should have prioritized getting up forward radar towers ASAP after pulling out of my early energy crisis. That would've let my Scorchers be far more active, and given me a comparative advantage in the occasional right-side skirmishes, and let me safely grab the low ground metal spots there.
8) While my Fencer pressure paid off in the form of forcing heavy porc for that stage of the game, I could've saved myself a lot of trouble later in the game by focus firing the second Stinger while it was under construction and bringing my third local Fencer forward to help.
9) The Stardust backing those advanced Fencers up paid off during RiposteRs clearing movement from the flank, but most of the value came from leaving Darts on low health. I should've supported the Stardust with a couple of Lotuses.
10) My frontline Commander should've been operating with queued area repairs after each build command. While I didn't really have much energy surplus, health on active fighting units was more valuable than factory production here.
11) My first Impaler died because I took too long between reinforcement waves from the factory. I really should've converted my rally point into a double rally that left less travel time.
12) RiposteR was vulnerable to a Scorcher runby on either flank after losing that damaged Dagger ball. Three Scorchers could have gone unobstructed to the factory and blown all the Caretakers. I could have discovered the opening on the left by examining the range indicators of known static defense and noting the gap next to the grey platform.
13) Whenever I killed a bunch of Daggers, I should've grabbed a couple of Scorchers from my rally point for a deep raid on the opposite side of the map. From spec view, it looked likely to work every time.
14) My factory mix should've had more Scorcher throughout, except perhaps during the early game. The Scorchers were working pretty well all game, but the need to back up Fencers with them meant I had little power to spare for sweeping raids.
15) RiposteR was afraid to push uphill against only four Ravagers. I could easily have been using the curve of the slope for an ambush. (I was, but it was insufficiently powerful)
16) I should've considered using a small number of disposable Darts as sentries or patrols throughout.

it's the right replay, just wrong name. Missing the detail of "nuke closed out the game", which is the bigger reason behind the apparent stall on the left flank(point 15, not afraid of uphill push, just knew my army was not my endgame)

In other words, the attempt to impale the Stinger failed because I targeted the Stinger itself, not the position of the Stinger? Would Force Fire have worked instead?