Jean - I suspect you may be misinterpreting Mrs Rosa's post - in all the correspondence we have had she has never claimed to have seen this bible - but relied I understand on what she was told by relatives (see her post where she confirms this) thus neither she nor I can give these all important details - the bible was last seen I understand in mid 1950's, current whereabouts not known for certain but suspected in an another branch of the family.
The mass production of cheap or free bibles started in the mid 18th C (eg S.P.C.K. and similar) - but relied on mass literacy to make it useful - for many households it probably provided the only book - the tradition of using the fly leave to note household events etc probably dates from late 18th C - later illustrated, large family bibles, of the early 19th C had pages set aside for such notes - the catch is that untill one looks at the actual entries one cannot be certain if contemporary with events or added generations later by a family member with an interest in genealogy.
Don't assume that every male produces hundreds of offspring - the Ballaugh Adam Cain is I think well documented on my site.
I would be very happy to be proved wrong - my background is in science where trying to disprove hypotheses is the modus operandi - you look for evidence which contradicts not just at that which supports.
The key link is that back to the Island as I understand and have never commented on the American descent - presumeably those with access to US censuses can trace the family from the early 1800's and see if any hints.