Solution for virtualizing a VB6 application [closed]

This is literally what App-V is for, at least for the client pain-points that you want to kick down the road.

https://docs.microsoft.com/en-us/windows/application-management/app-v/appv-getting-started

Backups for the database - other than forcing clients to disconnect so you can get a good backup, you're going to want to migrate to SQL to solve that (very important) issue.

Michael's comment is correct, that you should definitely rewrite this for this century. Since you have the source code, your company has little excuse to defer this cost. Considering this is a core asset of your company, why leave it so fragile?