option client_to_client '1'
and option topology 'subnet'
might be right config option you are looking for :slight_smile 
Check the configs from my configuration (and i can access any lan service/machine without any problems )
Kterak jsem si rozchodil (aspon doufam) openVPN (it is in czech, but configs might help, also that streamlined guide linked there was for me ‘save-the-day’ , especially firewall rules section ) …
Your fw rules seems to be defined okey (including the zone forwarding). To have some stats in luci for correspond vpn zone , https://wiki.openwrt.org/doc/howto/openvpn-streamlined-server-setup#tab__logging (without that it looks like no traffic at all)