Moreover, even on other models it will not work. Even new TL-ER6120 (version 3) could have same remote local network setup, but it didn't work. It is so weird, that tp-link doesn't want to add this...

I bet it is about IOS<->AP. Try to change wireless channel manually (6), change wireless bandwidth to 20 MHz (old IOS devices work poorly with 40MHz). I can only get 0.5 mb of download bandwith...

You can read about 3-MAC and 4-MAC-address models to understand, how it works:)

I had a problem with management hanging, because I did not delete VLAN 1 from ports, when changing VLANs, and didn't delete VLAN 1 interface. When I fixed it, everything started to be fine for me.

In fact, you can even update your switch with v3 firmware (20180201), because v1,v2,v3 firmwares are able to be installed on v1/v2 switches. It could be installed on hw v3, when it will be released...

Where does PoE come from? Are you sure it is not a problem of PoE-injector/switch? I met a problem with poe150s, when there is not stable electricity and there is some problem with power adapter, but...