1) What is the exact pronunciation of plural "s" at the end of words which have "th" ?
2) What is the difference between these phonetics ? "a:" , ">:"
It sounds like an 's' not a 'z'.
a: = arm, barn, farm
what you have as >:, though it's more like a backwards 'c', = bore saw, caught.
Lots of links:
Downloadable phonemic charts: