Strongly encourage you to try to accomplish your goal without any delete commands at that scale that causes vacuuming. Can you just create an empty copy and load the data to keep into it then point at the newly filled database? Truncate is OK.
This is really the best solution, especially if most of the rows are > 75 days old. This removes 100% of your bloat, allows you to keep the old data around in case something goes wrong, reduces WAL compared to massive deletes, and removes the need to mess with autovacuum.
Looping DELETE is the Dirt Simple option when the application is writing 24x7, when there's a lot of FK dependencies, etc. It also allows you to throttle the process (bash sleep between DELETE statements, or only purging a few old days per script execution and then only run the script at night).
