Luci is blocked from WAN, because in Luci you can do anything easily. However, keep reflashing is a bug. It should just give a deny message. This is done in lighttpd. We will check and get back to this issue.

SSH (port 22) is blocked from WAN too. You can open it on firewall.

Why we use 83 not 80 on WAN. First reason is to differentiate LAN and WAN access. Second, a lot of ISP just blocks 80 port, but not other port by default.