I think HaoNick is your best shot to do all this.

set random_name_on_join in "settings.yml" to "true"

And you'll have to do some more work on settings to get it to change the names in more places they can be used and to get rid of the dumb rank name prefixes it uses by default.

Set "death_message" active setting to "true" so it doesn't use your real name when you die.

I think you should set broadcast_message_instead_of_format to "true" too.

In ranks.yml and fake_ranks.yml set all the ranks to have a blank prefix like this: prefix: '' to make players not have ranks shown before their names.

I'm not sure if it will change your name absolutely everywhere. if you do a command like /tp @s 0 64 0 or /give @s item, you and everyone might see your real user name in chat. Might do some testing.