Ok, issue at least partially and painfully solved. Reboots were power related, but it looks like my tests/program/setup were too much for the 500ma supply from the store. To test I was trying to run 4 zones + a master at the same time. Hooking the pi up via the micro-usb be was a mixed blessing. The pi stayed up during the whole test, but the valves shut after 30 or so minutes. It seems my valves (Rain-bird CP075s) pull 190ma each, and with five running it was just too much for the transformer. I’m assuming when the Pi was running off the OSPi power, the power would dip, it would reboot/freeze, the valves would close, and the transformer power would recover. With the Pi independently powered, it went until the transformer burnt itself out 🙁 .
I’ve ordered a more power transformer from the internet and will be more careful about running too many zones at once in the future. Its still not clear if the wifi issues were related to the OSPi or poor reception. I suspect in at least some cases I was mistaking the wifi issue for a reboot/freeze since there’s no display hooked to the Pi.