I'm not checking the actual calculation but I find the result surprising.
We are discussing intersteller gas clouds and the crucial "length" with resonable parameters comes out to a jillion times less than a billionth of a meter?? This doesn't seem to make sense.
I'd have expected this to result in numbers that would actually separate "too small" clouds from large enough. Answers in 100,000's or much, much more meters is more like what I'd expect to see.
I don't get it at all is the probable conclusion I should arrive at.