Have you considered using a Cloud based file store for files you wish to share and synchronise? We have been using
OneDrive, it comes with the Office365 subscription for some time and we find it most effective, and resilient. In fact we have been using Cloud-based software and services for decades, all around the world. It is extremely cost effective, and flexible, particularly when staff are on the road.
For issue #2 - Run Wireshark on the server to see if the ICMP packets are even making it there. If it is a Windows server, it is possible that the firewall is blocking something. Check routing table on the remote client machine to ensure that the proper route is added with a lower metric for the internal network.
For #3, I do not believe there is a way to configure port based routing via the VPN client. The traffic will take the chosen path based solely on the routing table.
HTH, but let me know if you need more clarification on anything. Thanks!