Your notifications table is still massive. Compare, for instance, meta:
notifications | 1230140 | 316 MB | 581 MB | 897 MB
Try this (the first may briefly cause errors or read-only while it runs):
VACUUM FULL VERBOSE notifications
and
REINDEX DATABASE «yourdatabasename»
And then can you re-post the stats?
(looking at the other tables, your posts
table also has massive indexes - on meta we have 3933 MB
with only 674 MB
of indices. If you can take a brief window of downtime I would recommend VACUUM FULL VERBOSE
which will do the entire DB, followed by the reindex.)