"Can he be a single member LLC without me as a part owner and still have his initial business losses/depreciation apply to my W-2 earnings?"
Yes.
If you were added to the LLC, a multi-member LLC would need to file a Partnership return, which is a completely separate (and more complex) tax return. The exception to that is if you live in a Community Property State, in which case you could still file as a Qualified Joint Venture.
Although a LLC can protect you, most people mess up the protection my mixing personal stuff with the LLC. Another option is to just have a good Liability Insurance policy.
