Hi Lili,
I'd like to echo what Chiroptera just said, but by focusing on just one part of your post:
Lili writes:
However, based on the excerpts from his paper...
Exactly. Based upon what this creationist chose to quote from the paper, you've concluded it argues that isochron dating is unreliable. The paper does no such thing.
For me, one of the biggest mysteries of creationists is their extensive use of misrepresentation. Quoting out of context to make something seem supportive of creationism when it absolutely isn't is one of the most common tools in the creationist toolbox. Presumably creationists sincerely believe in all the positive qualities expressed in the Bible, especially honesty, yet to battle evolution they will pause not an instant to mischaracterize what scientists say.
To listen to creationists quoting scientists and scientific papers you'd think there must be a huge number of geologists who reject radiometric dating, of cosmologists who reject the Big Bang, and of biologists who reject evolution, but it just isn't so. When you consider that creationists have even quoted what they purport to be anti-evolutionary statements from as strident an anti-creationist as Stephen Jay Gould then it becomes obvious that their characterizations just can't be trusted.
Doesn't seem like the way to earn a ticket through the pearly gates.
--Percy