I highly advice against nfs mounts between a vps and home network, even with a static ip and over a vpn.
When you need data that’s on the nas at home on the vps, it’s best to place a copy of that data on the vps local storage. It can act as a backup as well and the original data can be kept safely at home.
What are you trying to do with this setup? Maybe we can find another solution for you.