i suppose the internet speed is decided by the ISP and the bell router. The wifi range might be increased if the tplink one is stronger than your bell router, comparing wifi parameters etc.

not sure, not listed on the tplink compatibility list either.

what about the wired connection? if only the wifi has the problem, you may try fix the wireless channel to 1/6/11 etc, sometimes updating the latest firmware may help.

possibly related to the IE settings, especially the proxy server restore settings etc, see instruction below. it;s also worth trying reset the modem to factory defaults....

i think your modem is using TC chipset, and it's limited to 8 wireless filtering rules

do you see DHCP pool list under internet setup, Lan?