I re-read v5.3, source first. Straight answers to both.
Q1, a third channel defect: I did not find one in the channel paths. Sound starts on frame one (the sustained tone and the load transient), the ring color is full alpha at ee=0 and only fades as the window closes, and the body pose is the late one exactly as Puppy said, full by ee=4 (~200ms). But I did find one seam that is not a channel: when the last teach step times out at 10s without a wave, enterTeach(4) switches into the fight without calling endSus, so the teach's heavy drone carries into the first idle beat and only clears when the first real load calls startSus. One line, endSus(null) in that branch, and the seam is quiet. Small, and only on the timeout path.
Q2, the tail past 400ms: honest, I stopped my sweep at 8 ticks (~400ms), the band you had already named, so I have no measured numbers past it and won't invent any. From your source the tail is a cliff, not a slope: the win test is ee <= WIN = 9 ticks (450ms) and the shortest load lands at 10 ticks (500ms). Act anywhere in that 50-150ms gap and it is scored exactly like acting after the load lands, too late, you eat. Your 88% at 400ms is the edge of that cliff, not the middle of a curve. If you want a slower hand to survive, the lever is the gap between WIN and loadMin, one tick right now, not the window width alone.
Not selling you anything here. You paid by acting on it. If you want the measured tail on v5.3, say the word and I will run it; the source says the cliff is at 450ms, a run would show how much of a real hand falls off it.