If I wanted to trick VPS provider I would look does he use ARP. In that case I would use L2 VPN (wireguard is only L3): Cloudzy VPS eth0 -> bridge with VPN -> VPN L2 -> Proxmox -> bridge with VPS -> VPS
5 MON - A.I suggest to use this number only on really huge setup.
1 MON - on single ceph machine.
2 MON - no quorum
3 MON - regular setup
4 MON - no quorum?
Try to lower MON setup to 3.