Cathredral Ceiling Insulation Question

My current roof is 23 years old. I have a cathredral ceiling that extends to the 2nd floor. The roof has Arch GAF shingles on it now with some problems. The North side with the vaulted ceiling has moss and black algea growing on every shingle, we have had leaking problems because of a poorley installed metal ridge vent and ice dam problems on the front eaves. There is 6 inches of insulation in the 2x10 roofing system with no baffles and a drip edge vent at the roof edge. I have gutters and there are some mold problems in the attic on the non vaulted portion of the house. My side boards are rotted because of moisture problems and need to be replaced. Most of the roofers didn’t want to deal with the carpentry issues. I’ve had at least 4 roofing contractors look at my roof and I get different answers on how to correct the problems. All agree I need to replace shingles and correct ventilation problem. Some agree the insulation needs to be replaced. I am considering having the plywood removed and replaced, filling rafter with the Corning high density C 30 insulation. No one has come up with a good solution for a rafter vent. The last contractor suggested a 1 inch rigid block of styrofoam over the batt. I called Corning and they didn’t like that idea. They said it was like putting a cover on a pot and the insulation couldn’t release moisture. My friend actually had a good idea I thought, take a tiger claw rod and pass thru rafter mate and push in place over insulation to hold in place. What do you pro’s think? One roofer recommended 1/2 inch fir plywood for the roof deck, should I be requesting a heavier sheet and do you use fir? I would like to replace the drip vent with a soffit vent. He also wants to cover entire roof with ice and water barrier. Do you guys think the baffled ridge vent is better than the rolled stuff? I’m sure you guys deal with this stuff everyday, any suggestions would be appreciated. I stumbled on this site last night and read a years worth of posts. You have a great site.

Normally on a home such as your what i do is this. First if you can put soffit vents in by all means do that rahter than the drip vent. SOffit vents flow much more air than the drip vent and the drip is used only where there is not an overhang to attach a soffit vent. Here is a few things that should help. If the insulation is moist it needs to be replaced. 2 adding baffles in the attic will help out with this type of ceiling. Using baffle style ridge vent is in my opnion a better way to go. I would have all the ventilation brought up to par when having the roof done. As far as using ice and water over the whole roof. I would not do that. To me thats the unprofessional way of doing things. It is an underlayment. I know of many homes without any underlayment that never have these problems.

Photos would certainly help.