Thought it was about time we had some of these.
1. Spokes do not "bed in" and need retightening after an initial period, unless it's a badly built wheel.
Just occasionally you get a soft hub shell in which the spoke heads can creep a little, but these are rare (the only hub where I had this problem was a very thin Sturmey-Archer alloy shell from 1951, which has flanges the same thickness as the steel shell; they often crack).
2. Spokes do not fail because they are too tight. They fail because they are too loose (movement leads to fatigue). The ultimate tensile stress of a spoke is way above anything the rim can take, and riding the wheel makes them go slacker, not tighter.
3. Spoke tension does not affect ride quality.
4. Plain gauge spokes are not stronger than double-butted. Their advantage is that the wheel goes out of true by a smaller margin should one break, because they are not stretched as far as DB spokes. But spokes don't break in a good wheel.
5. Radial spoking is not more aerodynamic, but it looks cool.
6. It makes virtually no difference to wheel strength whether your spoking is symmetrical or asymmetrical or which way round the leading and trailing spokes run, unless you have a good reason unconnected to the wheel itself.
Iif you think your fixie will throw a chain, you want the spokes to throw the chain out, not suck it down between the sprocket and hub flange where it will jam; so the "heads in" spokes should radiate backwards