This is *very* old version, not supported by the community for many years. Check https://www.postgresql.org/ to seecurrentlysupported versions.
You need to upgrade it.
Don't even think I'm in control of when -- or even if -- the customer decides to upgrade.
That being the case, do you have an answer to the question?
Those queries from wiki for table and index bloat estimation are for estimation only. In many cases they show very wrong results. Better (yet not ideal) approach is using pgstattuple extension (though I'm not sure it existed back in 2009).
Can you provide table and index definition and, if you can, some sample data?
Sadly, no sample data. (It's all PCI controlled.)
Index idx_item_mapping_rp7_y2016m03itemmapping_custom_userfield_801 has 40% bloat.