Manually flushing write cache on Windows

Yes - it's also called Sync, it's part of the SysInternals Suite:

Use it whenever you want to know that modified file data is safely stored on your hard drives. Unfortunately, Sync requires administrative privileges to run. This version also lets you flush removable drives such as ZIP drives.

Yes. Looking for sync.exe I found that there is a SysInternals program to do just that. I have not used it, but I have never found a SysInternals utility which did not work extremely well.

It can be down-loaded separately, or as part of the Suite.

Windows Powershell has the "Write-VolumeCache" command, and it does not require administrator privileges.