Heat Tape length for Incubator

I have outgrown my 50qt cooler incubator and will be making a bigger one. I got several questions i want to ask before i start building.

1. Will two feet of flexwatt be enough for a 120qt coleman cooler?

2. I had placed the heat at the bottom of the cooler. The temp was always higher on the bottom tub by a couple of degrees. Will placing the flexwatt on the side of cooler help with the temp difference?

3. I tried placing two fans but did not notice the temps changing. I connected the fans to a cell phone charger. Will connecting the fans to a speed regulator from coolerguys.com help with the fan speeds and temps?

Thanks for your help.