Well I got through the problems with Apache2::Module::get_config. Aparently the object which comes as the first argument to the method for the custom config directive is not where the config parameters should be stored. Looking back at the documentation http://perl.apache.org/docs/2.0/api/Apache2/Module.html, I can see that it is clearly shown that $srv_config is being fetched via a call to get_config from within the custom directive subroutine, and that apparently is where the config should be stored... but it does seem kind of counter intuitive to me. But no use second guessing that now, at least I got it.
On a positive note: before I discovered my mistake with get_config, I thought perhaps it was getting mangled by Apache2::compat, so I spent much of the day finding and jumping through hoops to get everything to run without that. Though that effort didn't fix the problem I was chasing, it will be better in the long run to not need Apache2::compat, as that would drag down response times.