Couple of questions...

1. Have had extensive rat and termite problems. Existing insulation (some put down in the 90's with some original - 1940's - 1950's?) between the joists is full of feces, tunnels, etc.

Should I remove all insulation and replace?
Probability of the old fiberglass having abestos?
Is blown cellulose more enticing to rats or termites? (Even though I think I found all rat entry points, it is an old house with other possible cracks and crevices). I was considering cellulose because of it's air sealing ability over fiberglass. I have no insulation in the walls.

2. My ceilings are plaster board. I have found rat urine stains on the board after remvoing some of the fiberglass. Do I need to clean these areas - and if so, with what??

3. For all electrical connections between and on top of the joists (junction boxes, ceiling fans, lights, etc.) - is it ok if the insulation abuts/covers the connection? I have no can fixtures - just regular ceiling boxes.

4. My 1200 sf Florida house has 3 large 3x5 foot gable vents with ridge vents on the newer roof. No soffit vents.

Would installing soffit vents be beneficial or are the gable vents sufficient?

I am considering installing radiant foil stapled between the rafters a few inches from the decking (not on top of the rafters nor up against the decking). Is this a good idea?

Thanks in advance for any help on my questions. This job, like others in an old house, has ballooned to a much larger magnitude than expected!

personally I don't care for cellulose because the cellulose dust finds its way into the house through all the small openings between the attic floor and the living space.
these installs usually leave the homeowner complaining of dust..but that is just my experience.

what you do want to do is to create an air barrier between the attic and livng space. it will be easier to do if the old insulation is removed, and can be done from in the attic and from inside the house. from the attic air seal any large openings..around stove vents,vent bath fans
from the interior caulk around light fixtures and crown moldings.
do any additional work in attic like sealing ducts with mastics, supporting the ducts. seal supply boxes to attic floor.

Install the radiant barrier single sided foil installed with foil facing into the attic space. I use button cap nails and attach rb to underside of rafters. you should also use rb on gable end west walls.
florida solar energy center has good info on rb

then insulate. I like batts..easy to move and work..easy to put back in place. just split the batts around wires and fit tightly in joist bay. (again personal prefrence)

I don't mix ventilation strategies..
gable end venting is a stand alone
soffit and ridge vents as next option
and lastly wind turbines..not pav's
but in fla you wouldn't want turbines.
that the first thing we lose in hurricanes!

if you do remove insulation leave the lights on
in the house and go into the attic..loof for light
from the living space below. seal these areas.
if light can get in air can move..hot humid
attic air is a bad thing in our climate.

best of luck.

Randy247 - the house has been rewired in the past - so luckily I don't have any knob and tube (just some a few remaining cloth cords).

energy rater_la- I did question one cellulose installer about dust - he said it wouldn't happen - I wasn't convinced as it seems inevitable in an old house. Re: air sealing, I have sealed via the attic all the A/C registers, electrical connections, and kitchen and bath vents. I should caulk anywhere I see dirty insulation correct? I have found a small line of dirty installation where the top plates are in the attic - should I seal these as well as the perimeter top plates? That will be a lot of caulking, but I am determined to lessen my energy bill. Interior, I sealed all outlets and switches.
Why support the ac ducts? Mine are laying on plywood on the attic floor. Is there a radiant barrier you recommend? Would installing rb directly against the decking - between the rafters - be ok? I had it installed on rafter bottoms, but after years they sagged, got torn, and were "superhighways" for rats. Great idea about turning lights on in the house to check for leaks in the attic.