Hey John,
*made in china*... well there's your problem. LOL
I wouldn't run any of the power wires through the 30a fuse holder. The holder was probably designed with a 30a max load in mind... not a 70a.
Run the load wires directly to your tyco relay and you should be fine (pins 30 and 87). They are the switched power for the fans and they carry all the current.
Also 10ga is kinda on the line for 70a, so keep an eye on it... make sure you're using a good multistrand wire (lotts of little tiny strands can cary more current
safely than the same gauge wire, with only a few big strands... the trons actually move over the surface of the wires strands, not "through" them as is commonly thought)
The little signal leads that energize the coil shouldn't be carrying any kind of current to speak of, so they should be fine (pins 85 and 86)
D
EDIT: Also another way to ease the load would be to (and I know you wont like this... lol) wire in two controllers and relays so that each fan has its own circuit. Then set the temp sensors to come on about 5 degress apart so one fan is already up to speed when the other one kicks on. (they only draw max current for a few seconds, as they are spinning up to speed. Once they're up and running, they probably only draw 10-15a for a constand load)