I can't grant my friend permissions because it thinks that it's a separate arguement in the command, doesn't work with quote symbols, or declaring a symbol with /lp user user\ name

Because you cannot have a space in a mc name

https://namemc.com/name/squirtle%20fanboy

Your "friend" is either full of crap, pulling your leg or your running a cracked server.

Bedrock clients allow spaces in usernames

The error message you're getting actually has nothing to do with the username.

parent friend isn't a command. Perhaps you meant parent add friend?

But the command /lp user "squirtle fanboy" permission set nukkit.* true doesn't work either.

Set allow-invalid-usernames to true in your config and restart the server. Luck's commit above will make that default for new installations.