1) The naming is absolutely fine, just as SwDevMan81 stated.
2) Absolutely, If WCF gets outdated in a few years, you'll only have to change your DAL.
3) The rule of thumb is to ask yourself this simple question: "Can I think of a case where I will make smart use of this?".
When talking about your WCF contracts, yes, definitely put those in a separate assembly: it is key to a good WCF design (I'll go into more details).
When talking about an interface defined in AssemblyA, and is implemented in AssemblyB, then the properties/methods described in those interfaces are used in AssemblyC, you are fine as long as every class defined in AssemblyB is used in C through an interface. Otherwise, you'll have to reference both A, and B: you lose.
4) The only reason I can think of to actually move around 3 times the same looking object, is bad design: the database relations were poorly crafted, and thus you have to tweak the objects that come out to have something you can work with.
If you redo the architecture, you can have another assembly, used in pretty much every project, called "Entities" that holds the data objects. By every project i meant WCF as well.
On a side note, I would add that the WCF service should be split into 3 assemblies: the ServiceContracts, the Service itself, and the Entities we talked about. I had a good video on that last point, but it's at work, i'll link it tomorow!
HTH,
bab.
EDIT: here is the video.
