I'll fix this LDIF for you, although I don't know the answers to the rest of your questions.
$ cat add_meta_backend.ldif
dn: cn=module{},cn=config
objectClass: olcModuleList
cn: module{}
olcModulePath: /usr/lib/ldap
olcModuleLoad: back_meta
olcModuleLoad: back_ldap
olcModuleLoad: rwm
As for olc attribute names, you can trivially grab these out of the source code. Or, you can use slaptest to convert a slapd.conf to cn=config to see the corresponding configuration.
--Quanah -- Quanah Gibson-Mount Product Architect Symas Corporation Packaged, certified, and supported LDAP solutions powered by OpenLDAP: <http://www.symas.com>