For the USB I have placed it on POE+ swtich. I don't know it the AP-303H takes the POE+.
I also have posted a couple of days the question:
But I have not find a right pacage, only found something for a Hub.
Also should it be nice to also have POEenabled on ETH3. This is possible when powered with POE+. On stock firmware it works, now hopefully to find if it's possible for openwrt. I think I first need to identify the POE controller chip.