I found the "better way" I was looking for! Actually, it is exactly like I had it set up before, with two small additions:
1) in the /etc/httpd/conf/httpd.conf file, the "Listen" directive is actually 2 lines long...
Adding the line with the 127.0.0.1 keeps ISPConfig happy.
2) Do the same thing in /etc/httpd/conf.d/ssl,conf for port 443:
Now that everything runs like it should (I hope) All I have to do is figure out how to administer the resellers/clients/sites. Should be fun!