I can't offer insight to all your questions, but here's what I think:
Your coach choices are good ones. Our list was Tiffin, Winnebago, Newmar. If you've got more $$, look at older Foretravels.
I am the wife and do ALL the driving of our 40' DP. Personally, I don't want to go longer. I think some corners are tricky as it is. You are right that many parks cannot handle big rigs, especially older state parks. We actually bought a 22' B+ to take to Alaska two years ago. Worked great, kept it to use for east coast travel and when we want to make a quicker trip somewhere.
We had a 37' with a tag axle before. I didn't notice any problems with it, other than tires and it had to be maintained, but it worked for us. Our current coach does not have a tag.
I love my washer/dryer. Wouldn't leave home without it.
We also tow 4-down. Towing a 2003 Sport Trac for 9 years without a hiccup. Bought a dolly once years ago. Couldn't get our car on it with the ground effects. Modified it to be able to use it and didn't care for the way it worked. Our preference.
Monacos and Fleetwoods are still being built. Those companies were bought by Allied Specialty Vehicles and they are being built in Decatur, Indiana, as is the American Coach line and Holiday Rambler, too.
Here is a link to a website that gives a lot of information. I would not use it as my only source, but it will work for a lot of your questions, plus it has a good bit of finanacial information.
RV DreamsGood luck!
Dale