Can someone answer these questions about about tax exemptions for foreign-owned Delaware LLCs:

According to several sources:
"Non-residents of the U.S. who are members of an LLC and who are not otherwise subject to U.S. federal income taxation pay no tax in the U.S. if the LLC's income is from non-U.S. sources and the LLC carries on no business in the U.S."
I have a single entity Delaware LLC, I am a foreign non-resident of the US and my LLC does no business in the US.

My questions are:

- what happens if I add a second member to my LLC and it is no longer single entity? Does it lose its tax exemption?

- what if add a second member AND the additional member is a US citizen?

- How much would my LLC be taxed?

- Is there somewhere I could find additional information on LLC taxes?

Thank you.