My boyfriends friend is always rude to me: Advice?

Start to speak to him how he speaks to you. If he makes a wiseass rude remark, match it.

A few months? Y’all barely know each other after a few months.
Honestly, slow down. Saying your “I’m love” after a few months is just unrealistic. It’s impossible to completely understand each other in that about of time. You sound very young & there’s nothing wrong with that but your focusing on the wrong issue way to fast. I’d advice getting to know each other for a long period of time before you start delegating specifics such as this.

Then rude guy isn’t allowed in your home. End of story.