Sync Gateway can run on any port that you choose as long as you have permissions on that machine to do so (Ports 1 - 1024 generally have more restrictions about them from the OS than others do). As far as NGinx, I don’t see how it will be a problem if it is set up correctly. Since it is SSL all it can really do is tunnel the connection to the end server (Sync Gateway) but I’m not familiar with the particulars of setting that up.