I have my old doge wallet backup but there's no doge left in them. Do I still get clams?
No. Obviously the wallet.dat has to contain private keys that hold funds. DUH!!! OTHERWISE HOW WILL THEY STEAL YOUR MONEY.
You don't need to have doge to claim CLAMS. You just need the private key of the address to claim. Just ensure that you have used the address to do transactions before the date mentioned in the OP.