W8970 can support 3G USB modems and USB Flash Disk also. 3G modem list you have to search on TP-link website I've never compared these devices and I can't say anything about wireless range these...

Do you have ADSL synchronization on the router? Give us screen shot from Status tab when you have line in ADSL socket

Wired connection between devices is the best solution for you. After WA5210G you must set as typical AP

You must remember that password is not the only method of security our network

Very important in this mode is signal level between routers. You must remember that transmission is bidirectional.

[quote]Need at least 150Mbps [/quote] I confirm it. Max. speed on this router is about 22-25Mbps in 802.11g radio mode.