There are so many options it is almost impossible to know where to start!
Which distro is the VM running (is it even Linux)?
If you want the VM to use the host’s VPN then you will need some routing and perhaps NAT/masquerade. This is non trivial to sort out. Can the VM have its own VPN connection to your supplier?
You are starting to reach the point where VLANs/subnets and separate routers (real or VM) may be required. Depending what you use as your ISP router, we might be able to get a solution together - so what model is it and do you have any switches?