I was most interested by your ace in the hole. Antifreeze. I would
be interested if anyone has knowledge if Antifreeze would pose the
same danger to house animals as poison does. (snip)

In any mammal, including humans, ethylene glycol (the major component
of earlier generation antifreezes) will convert to oxalic acid in the
body which crystallizes in the kidneys, causing a painful internal
bleed leading to death. (A few humans have been saved from same with a
kidney transplant). The sweet odor and taste of it attracts animals and
even small children to consume it. It is one of the major causes of dog
deaths in this country. (the newer antifreezes use propylene glycol,
which is far less toxic).
The Warfarin products that some rat populations are resistant to is
believed to be due to the emergence of a digestive bacteria in the
target rats that produces large amounts of vitamin K, which counteracts
the Warfarin. I believe some newer baits have been formulated with an
antibiotic that kills this bacteria so the Warfarin can do its work. I
do not know the brand name, or where to get it.
I have used a Benjamin .22 pump air rifle with some occasional
success.-Jitney