Just some thoughts - I am not an expert:
- Can’t you do it so that the 300M acts as the “main” router and set-up the Netgear as a repeater via the LAN cable?
2, If you tether your phone by cable you can surely turn the wireless off on the AR300M (in firmware V3 it’s under “wireless”) - Whilst I can understand you wanting your full-speed, 34Mbps is very decent IMO.