Without seeing all your rules it's hard to say 100% but it could be that earlier rules in iptables are acting like a catch all, and traffic isn't getting to the forward rules you've shown in your question (this would explain why you're not seeing any data).
As per MadHatter:
Put your two audit rules first, and they should be fine.
Another approach:
Consider using the -j option, which is explained here:
http://ipset.netfilter.org/iptables.man.html
-j, --jump target This specifies the target of the rule; i.e., what to do if the packet matches it. The target can be a user-defined chain
(other than the one this rule is in), one of the special builtin
targets which decide the fate of the packet immediately, or an
extension (see EXTENSIONS below). If this option is omitted in a rule
(and -g is not used), then matching the rule will have no effect on
the packet's fate, but the counters on the rule will be incremented.
This might serve as a good starting point for you:
http://www.linux.com/learn/tutorials/305767-bandwidth-monitoring-with-iptables
After a rule is matched, the -j option invokes a jump to one of the
custom chains.