About article "IP fragmentation fails..."

The article "IP fragmentation fails and fragmented packets get dropped" at
https://access.redhat.com/solutions/1498603
is good. I have some questions:

In the Root Cause section:

(1) "A bug has been added to address this for RHEL6.6" means a bug fix has been added?
(2) If the global counter is updated less than the per-cpu counter, isn't the global counter lower instead of higher than what the correct value would be?
(3) How can the per-cpu counter be negative e.g. -130k? Value overflow?
(4) Is it possible that more than doubling the the IP fragmentation thresholds is needed? Since the required memory is so small on modern servers, why not give, say, more than 10 MB?

Thanks a lot.