Good dtuff, thank you, but I was getting "division by zero" so I wrapped relevant code of proc_FilltblIndexUsageInfo in a CASE:
CASE WHEN dbo.Uf_GetindexSize(si.index_id, so.object_id) != 0 THEN
CAST((user_seeks + user_scans + user_lookups + user_updates)
/ dbo.Uf_GetindexSize(si.index_id, so.object_id) AS DECIMAL(10,2))
ELSE 0 END AS IndexUsagetoSizeRatio