A: Enable webhook mode in the config file
A: No, and it is not planned to make it work clientside
A: No, Such a feature would be very likely to hit discord's ratelimit and would cause problems with the normal functionality of the bot. Closest you can get is the command log feature (showing which player ran what command) and creating custom commands. You can also grab an execute command, allowing you to run anything with it (https://github.com/ErdbeerbaerLP/DiscordIntegration-Addon-Repository)
A: Turn off vanilla whitelist, it is a different system
A: Turn off vanilla whitelist, it is a different system