I wish that I could help you with your problem but I am new to DNN and YAF and am still learning it.
I had some similar problems also but different error messages. My errors had to do with the default.config file. I changed the name to web.config and put in my connection strings correctly I think because I received no errors debugging for the connection string.
but I did get this when i tried to launch the "http://localhost/install/default.aspx" in a browser:

I believe it has something to do with the virtual directory for YAF not being an application but I don't understand why. None of the installation instructions indicate that we need to make it one. Also, if it is a module under my DNN website, doesn't it reference the core DNN directory as the application?
UpdateHere is what I get when I try and compile it:

Please Help.