Is it legal for my landlord’s boyfriend whose name is not on my lease to contact me about my lease and money owed?

It is acceptable for a landlord to utilize an agent. If the landlord's boyfriend is acting as agent, you might want to have this confirmed by the landlord in writing. If the landlord provides a statement acknowledging this, it helps protect you in the event something happens between the two of them. I doubt there is a written agency agreement between them. Written confirmation helps protect you. I would never pay the boyfriend any rent unless clearly instructed by the landlord to do so and demand such instructions in writing, otherwise I would always be sure to pay the landlord as the landlord instructs according to the lease, and any notices required or needed to be given, I would also be sure to give them to the landlord directly. It is acceptable as a matter of agency, but as a practical matter, these things don't always work out. You should consider protecting yourself first.

Yes, if he is the agent/representative/employee of your landlady. Pay her directly the day before your rent is do and you will never hear from him again.

If he is working for your landlord, then yes it is legal.