It won't matter to loosen one at a time and re-torque - but do it in the order of torquing indicated by many sources. Here's some discussion of someone who has given it much study.
http://www.fordgarage.com/pages/tighteningsequence.htm
Generally torquing is kind of the "proof of the pudding" for fasteners. If a fastener survives torquing, it will survive any normal stress put to it in service.
I would use the Permatex "spray gasket" on that water pump outlet pipe joint. Unless you're going for fine point - in which case you want to even forget the match-stick trick. The joint is between two machined surfaces, is relatively small between the bolts, is relatively fragile compared to most torqued head bolt locations, and a thin layer of spray gasket or even polyurethane spray will probably take care of any sealing required.
One opinion - put your money in the cup as you exit.
Joe K