well thats odd it doesnt ask for a product key. I dont mean to insult any intelligence..but i assume you have tried deleting the configuration folder. then going into adobe extension manager and deleting any orphaned extensions there, then re-create the configuration folder by loading up dreamweaver, then closing it and installing ONLY the digital file pro, after which create a new project in dreamweaver with ONLY applying ths digital file pro server behaviour?
I dont have the standalone version, I only have the universal email and some other product that includes the digital file pro..but i assume that even though integrated that it uses exactly the same code that dreamweaver uses for all the dialog boxes to set your behaviour up?!
again with the products I own, I never have problems installing or using the products, my only flaw is that I need to learn more about php and mysql to have a better understanding on how to use these products to a greater potential. and in my experience the technical guys here on the forum and (when needed) the one to one ticket support they have always helped me fast and always helped me to understand to the extent of what my own intelligence can cope with :)
its a shame that you are losing (or lost) faith in the products but from my experience of using them for the past few years that they are of a high standard. All I can hope for is that a solution can be found fast for you and so that your projects can be delivered without clients getting frustrated.
I wish i could troubleshoot with you but since i dont own the standalone version of digital file pro it would be hard to.
Perhaps ultimately (and since webassist offer a 15 days refund policy) you could purchase universal email or any other product that includes digital file pro) try that version, and if it works then you will find out more about where the problem is caused..and if you still have a problem using universal email etc you can at least identify that its something else rather then the actual product and still get a refund on that product while you look at your options.?