you could use a Dual WAN router like thishttp://www.newegg.com/Product/Product.aspx?Item=N82E16833124160
configure it as redundant connection. If one fails the other take over seamlessly.
you could use a power timer that turns off the power to you main modem at 2 am and turns it back on just before 7:55 am.
turn the fast modem off at 8 am and then back on later.