You could install OpenWRT and install a hotspot package, e.g. Nodogsplash, CoovaChilli or WiFiDog. or DD-WRT but you have to check hardware version of your WR740

Mistake - I said about static IP and gateway address from main router. For example: Main wireless router IP - 192.168.1.1 (this is your internet gateway) DHCP Server 192.168.1.2 to 192.168.1.100...

DHCP Server but remember about gateway (IP addres from main router).

This signal isn't very strong and I can see a lot of radio noise in the air. In the log I can see also problem with DHCP server. Sometimes help switch on DHCP Server on the repeater with main gateway...

Maybe, I can see it in latest firmware in AC2600

I prefer screenshots from measurements for example inSSIDer