it is normal that MAC address is different, LAN interface has for example: AA:BB:CC:11:22:33 address, WAN interface has another AA:BB:CC:11:22:33, Wireless interface another MAC AA:BB:CC:11:22:35
it is usually WAN MAC +1 = LAN MAC +1 = Wireless MAC
I am not sure if repeater will give you signal that is good enough, maybe it is better to go for Powerline + WLAN adapter
https://www.amazon.de/s/ref=nb_sb_no...powerline+wlan