OWCH. Did you torque to foot lbs versus inch lbs or something? It's a monumental difference. I have a Harbor Freight in.lbs wrench, so there's no telling how accurate their junk is. I think it's ok so far.
Not sure how much luck you'd have looking for a salvage cover instead of buying new, but might be worth a try. Car-part.com is a good salvage yard network that might be able to hook you up for far cheaper than a new one.

 

I need to repair oil leak at the rear valve cover. Does anyone have DIY steps? Thanks.