What do you mean "clone wifi network"?

If you have selected "Access shared storage with password" you have to settings login and password in User Account Management area.

Give me screenshot from USB Settings. Is the router sees the drive?

I think that problem is in your electric installation. You can check internet speed when adapters are close to each other (in this same room). Very often in electric installation are very large...

Better will be Gargoyle than typical Open-WRT- http://ecco.selfip.net/gargoyle-pl/attitude_adjustment/ar71xx/

WISP mode is typical converter from radio interface to cable interface (ethernet). I can't understand your idea with phone connection?