12down, 2up, just yesterday, which required two DSL phone lines, each delivering 6 megs down and 1 up.
Are these combined into one network, using a dual wan router or kept as two different connections.. because linking is not easy.. did you ISP do a bonded connection with specialized equipment??
Anyway it seems like the problem is the TC.
It hasn't dropped; been nearly half an hour now.
Ok.. so with no TC running all is good. Pretty strongly points to TC issue.
What model exactly is your TC?
If it is the latest one.. it can be troublesome on the WAN port.. as can the older ones using 7.6.4 firmware.
So I would advise if you use bridge mode for TC setup.. plug from the modem LAN to the TC LAN port not WAN.. it is possible in this setup to use any LAN port.. so test all three.
The TC must create a wireless network and it should be setup to not interfere with existing wireless.. so I recommend fixed channels and even use two different names for the two bands as a way of reducing the amount of swapping going on.. fix the main router wireless as well.. they will normally only use 2.4ghz.. so set one to say channel 1 and the other other to 11.. that gives the best separation.
I'm looking for software that will monitor my whole LAN, telling me how much data, and what deviceis using up bandwidth. Can't find it for Mac, only Windows...
If your TC is Gen4 or earlier PeakHour works very well. And as long as the modem is also the router.. it will not matter so much even with Gen5 TC.
Apple removed SNMP from Gen5 hardware for no known reason.
Tracking usage and bandwidth is my speciality.. and I strongly recommend Gargoyle firmware on a Netgear WNDR3800 .. or Dlink DIR-835 .. both are pretty well equivalent.. and pick even a second hand WNDR3800 can be cheap.. I cannot even give you the URL to gargoyle otherwise Apple deletes my post.. but just google.. Or email me.. it is open in the profile.
It might be a complex setup.. but you have such a limited internet bandwidth you should go to great lengths to protect it.. the advantage of gargoyle is setting quota and throttles.