Good Questions!
1.
Cant add to the previous answers!
2.
Modern, metal sparred, rotor blades are/were cheaper to make with a constant chord as they only needed a twisting of the Spar to get the correct Wash-In/Out. In the case of Whirlwind/Wessex Blades, his was almost literally done in a big Vice-type machine that was manually twisted/tuned. The leading edges and pockets were then attached to the Spar and gaps caulked.
In the case of Carbon Fibre blades, I believe it is now easier to lay a constant chord pattern than a variable chord pattern, though I stand to be corrected. It is of course possible to lay whichever pattern you like, but time, money and difficulty all come in to play when laying large tracks of strands/mats/ribbons.
3.
They Failed! Wooden blades were fine for low weight and low rev rotors of the time but would not be able to withstand some of the more powerful strains of modern times. They were also susceptible to various warping problems and diseases in more exotic climates. Wooden rotors should not be confused with wooden airframes or wings. Wings don’t do all that twisting and bending per Rev.
4.
“For every action there is and equal and opposite reaction”, The same works for Rotors – If you make the Head rigid you must also make the surrounding structure hard enough to support the Gear (Actuators) to make those movements. and then the airframe needs to be strong enough to support the rest!
In other words; There is no sense in building a Tank if it is going to be used like a Pram!
Hope this helps