1) yes, the downside being that all of your beers will be carbed the same. Iff your anal about such things you would want to carb each beer as appropriate for each style of beer, otherwise just pick a good middle ground that you like and carb them all the same.
2) If this is the case, you will want a secondary regulator. Set your primary to 35, connect a "Y" to it one going to a hose/connector for force carbing (also useful for a counter pressure bottle filler) and another going to the fridge for serving. Have the secondary in the fridge set at serving pressure and going to your manifold or what ever other distribution system "Y"s "T"s etc your planning on.
3) Teflon tape where fittings screw in. Oetiker clamps for hose barbs. Turn on the pressure and spray with starsan or liquid soap that will bubble if there is a leak.
4) I have a couple of these: http://www.harborfreight.com/cpi/cta...emnumber=93979
there are two openings on one side as shown and one on the opposite. Unscrew the plug and use a nipple to connect tow together and you would have a five way splitter. Not the most elegant but it would work. Alternatively Search beverage factory for "manifold". looks like they stock two and three way blocks that can be chained together for whatever number you need.
5) what plastic dohickies?