Third time was the charm; I went back out with charged batteries and the skies were clear. Tried different exposure times and found that I could reliably get about a minute without trails at 200mm. Better polar alignment would surely help here; I was just putting Polaris in the center which isn't quite correct.
Spent a lot of time fussing with my intervalometer; I haven't used it in a while and I had to remember its quirks (like the interval between shots starting from the beginning of an exposure, not the end of one).
Ended up getting 17 1' subs of Andromeda before I called time and went home. I won't post the result here as it's nothing noteworthy, but it's encouraging.
Hey, I've noticed the screws for Alt/az adjustment are both a bit sticky and a bit rattly when loosened, makes it hard to do really fine adjustments. I'm not shelling out $200 for WO's base (especially since a redesign has reputedly made it difficult/impossible to switch between low and high latitude configs) but has anyone gotten good results sticking some white grease or something on the threads to smooth things out?
In order to properly polar align, use an app like PolarisView on Android or Polar Scope Align Pro on IOS. These apps will show you where to place Polaris in the polar scope's graticule. Make sure your rig is level as well.
RTFM on the intervalometer.
The best way to make adjustments with the stock alt-az mount is to have it tightened down to near lock on both azimuth and altitude, but you can still make adjustments. This way it's easier to compensate for the backlash, because the backlash travel won't be so far when you tighten down, and you can guesstimate where you need to be so when you tighten down fully, Polaris will be where the polar app is telling you to place it on the graticule.