Making do the default for all file/folder types. How?

Some applications still manage to call explorer (I hate that).
How do I make dopus to completely take over explorer?

It depends on the application and how it is launching folders but the problem is often this:

Most applications will launch folders using the ShellExecute or ShellExecuteEx function. A few applications incorrectly specify the "open" verb explicitly, instead of leaving the verb blank in order to get the default action, and this will cause Explorer to open instead of Opus. It's something you could ask the application developers to fix, with this as backup/justification for your request: ... 32224.aspx

It's also possible that some applications are explicitly calling Explorer.exe, but that is far less likely than the above.