Dialog forms suspend all code execution in the calling procedure. Can't comment on your first point without knowing what you deem to be the active form. If you mean the one that called the dialog form, then it is not active any more. If you mean the called form any code behind it should run as long as it doesn't call another dialog. The vbe behaviour is normal for what you describe. If you're testing, why can't you just deal with the dialog like everyone else will have to? If you could test the db in a way that users will never be able to then you're not really replicating normal user actions so that will be misleading. Not sure what you want to do when a dialog is open, but if it's related to another app then minimizing Access or having a second monitor might help.
The more we hear silence, the more we begin to think about our value in this universe.
Paraphrase of Professor Brian Cox.