If you have to machine your rotor, which I think is a must for such a big craft, I'd try to add some kind of mechanical limiters for the blades. Something, such as a set screw, which limits the flapping in each way, at least on lower side, to avoid blade strikes and (if you add on the top side too) excessive blade flapping during takeoff and particularly hard maneuvers.
Your numbers seem to make sense, and such rotor loading is very good. BTW, which guru are you referring to?
For the blade chord, generally speking, the larger the craft gets, the higher aspect ratio you need. Smaller craft tend to work better with wider blades, but as size goes up, they seem to like thinner chords. I'd start with something like ~10:1, which seem a good middle point.
Be careful with the rudder! If your fuselage isn't long enough to put the rudder after the rotor, then you may have problems to have enough area and rotor clearance (some people use small rudders under the craft to avoid this, even historic aircraft).

I can't help you with servos, but as you may know, use powerful stuff there. An average servo may even break under certain loads.
For the rotor prerotation, you have several choices. The air flow idea has been tried before, at least in full size craft, with not so good results. I personally dislike it.
- For small craft, a flat spring wound around the rotor can do the trick. It can be installed so that it releases it's energy only when you tilt the rotor full back and then it doesn't affect the spin during flight.
- For medium-big craft, a small motor seems to be the best solution, but it adds weight where you don't want it. Perhaps you could even mod a strong outrunner motor so that it shares tha axle with the rotor, and spins it during prerotation without any external gears.
- For big autogiros, you can use a flexible coupling from the engine. A very realistic method, perhaps even lighter, but not an easy one. For the coupling, you can try one of those that come with chinese dremel-like tools (they cost like 15€ or 20$, so you can give it a chance) and include a flexible coupling which might be shoul be more than enough to move
I hope this is of some help.