1. Freewheel threading. Singlespeed freewheels with 16t or more are ISO/British thread and 15t and less are Metric. Fixed gear flip flop hubs have ISO threadings on both sides but the "fixed" side have threads for a lockring.

2. I don't think the difference will have too much effect on how much or less you need to re-dish the wheel.

3. A freewheel hub with ISO threading will accept a track cog and a singlespeed freewheel with no problems.

4. Not sure what you mean. Cog/chainring thickness? Chain thickness? Pitch? Please elaborate.

5. Suicide hubs can be safe if it is done properly and have two brakes on. Loc-tite and bb lockring are recommended.

6. Cite the Sheldon source please, not quite sure what you're referring to.

7. I'm no physicist, but I don't think the amount of torque will change just because you are riding fixed gear.

8. Axle spacers should be available at your LBS or bike co-op.