My Mac address is gone away ...

Hi, to everyone and before I start I preheat that everyone can advise me
My Wi-Fi Network is like in the diagram above My server is MikroTik 2.9.27 I’m using HotSpot Authentication By Mac and HTTP CHAP and HTTP PAP, I create a user name for every client in my network.
I configure a DHCP so I can send to users the DNS’s IP and I also Leases for every user one IP from a pool start from like in the diagram from 192.168.1.50/24 to 192.168.1.80/24
I Lease for every user an IP so I can control the user speed from queue.
This is my configuration and everyone is happy as simple as that… life is easy
Until I configure a new user that weak me up and I see the ugly face of the real life
He trying to scan and get the user name and IP and mac and login with that user.
Now can anyone can help me with two things, or I have to go and get rid of him and kill him
First: I wana something can hide mac’s and users can’t see each other, and block sharing files just I want them to serf the internet.
Second: what I can I do after he know every mac and users name I changed them all and new passwords but the mac’s how I can block him with his ability to change his mac and his knowledge of my clients mac’s
And I wana your help for any idea I’m still beginner in this felid.
And I’m truly thankful for everyone can help me… :slight_smile: