Re: If Americium soirce was moderately damaged how much would be respirable?

Generally your information is correct.  I would think very little, if any, 
would be respirable from a scratch in the surface.  You may produce some 
contamination however but I doubt there would be much to breath unless you 
specifically tried to inhale it.

I am less sure about the chemical form of the americium as it relates to 
absoption in the gut.  Basic radiation safety concerns with alpha emitters 
(like Am-241) is to limit their intake of any kind (ingestion, inhalation 
or injection)

Even the small quantities of alpha emitters like that found in smoke 
detectors, as we learned from the alpha partical emitting Po-210 poisoning 
of the spy in England, can be harmful as it only takes a small amount 
inside the body.  So care should always be taken with these materials.