hello great site

my house (30 yrs old, toronto canada cold climate) has two above ground floors, one half way down ground level and one basement, looks something like this

(upper floor ) =============> ----------
(ground level) ====> -----------
(half sunken ) =============> ----------
(basement ) ====> -----------

so im explaing this because i have two different seperated roofs, (upper floor and ground level flloor) we have a pest problem (mice i think), so i went up to put some bait and i found some issues.

The upper roof is very shallow (4ft at peak) and on one side of the roof the sheathing is pretty black (roof was done recently and went up today bacause it was raining hard all night and day and no apperent leaks), on that side of the roof is the bathroom with a window but no fan ventalation and a natural gas furnace and hot water vent, the insulation up there is dirty on top and its r20 fiber glass (this region should have R32) with paper down, the insulation is tucked up to the sheathing blocking the soffit vents.
This part of the roof is 525 sq ft (+95 sq ft soffit area, not sure if you count that) so i went up and installed some foam baffles where the soffit vent were, do i have to install those baffles all the way around the perimeter of the roof? There are two roof vents (about 5 inch diameter hole in sheathing each) and 5 soffit vents around the perimeter (about 120 sq inch each). The soffits vents and roof vent seem to be in good shape themselves (no lint blockage). I know your supposed to have about 1:300 half in half out but i've looked around the neighbourhood and see that many people only have one roof vent in roof areas as big as mine with more soffit venting (like mine). do i need more venting you think (snow build up on roof is issue) (by the way the attic entry needs to be insulated better and i will do that before winter, maybe losing alot of heat and moisture through there)
The other roof is the bigger problem, last year for the first time in many years we a giant ice dam on one side of the roof above the kitchen, there is no fan venting from the kitchen, and the plumbing stack is right near the ice dam. the lights in the kitchen have rust in the fixtures and there is a small leak about 8 feet from the exterior wall, i have yet to venture off into this attic space but i know the insulation is probably blocking the soffit vents and there is only only one roof vent same style as in the upper roof (otherwise i think theres adequate soffit venting) ( this attic is larger - 900-1000 sq ft) the insulation is the same as the upper roof (R20). How do you insulate and vapor barrier the plumbing stack and how the hell do you find out where mice are getting in? Also should i take out existing insulation and place a poly urethane vapor barrier and then reinstall and insulate more? (old insulation is about 8-10 inches thick so i think its in pretty good shape, how can i tell if tthere is asbestos in the insulation)

Sorry for the long post and thanks in advance for any help.

 

so i went into the second attic tonight and the soffits are really blocked and insuolation is sitting on an angle on top of another insulation piece where im having the ice dam problem, also the attic is not as big as i thought becasuse one piece goes over the garage and is not part ot this attic so the second atic is only 675 sq ft.