"1---Was told that this is a 1973 house, (county records on the
internet say this as well). However, I have found strong evidence that

this house was probably a total remodel of an older house built maybe
10-20 yrs prior. A)--there are exposed areas of the sheathing (siding)

in several places that are easily observed (where the exterior cedar
shakes don't quite cover). This sheathing is shiplap. I understand
that shiplap sheathing was replaced by plywood or particle board long
before 1973. Also, the foundation has lines etched all over showing
that before the shiplap boards were used as siding, they were used for
cement forms for the foundation. This is supported by the cement
stains seen on the shiplap boards. "

If you have a claim as to the age of the house being misrepresented, I
would think
the direct and obvious claim is against the seller, not the home
inspector. The problem
of course is proving damages. You could consult with a real estate
agent or appraiser to
get an opinion as to what effect this has on the appraised value. You
may find there is a
negligible or zero effect.

"Obviously, this devalues the house because it is an undesirable defect

that cannot be fixed....who knows what condition the framing / subfloor

is down there after 30 yrs of unventilated...the old garage floor is
cement and could be damp. I'm guessing there is around 4 inches of
space beneath the 2x8 floor joists and the cement floor....not enough
of a void to ever put in access...ie cralspace. "

I'd do what is necessary to get this ventilated. To do that, you'll
have to cut holes in
the foundation which will give you the opportunity to make them large
enough to have
access. Then you can assess what conditions are under there. You may
be lucky and
have no damage. If there is damage, then you can assess how much and
decide what
to do. IMO, it's unlikely that you'll find enough damage to warrant
the cost of litigation on the
chance you could prevail and get a decent recovery.