Yes, forming an LLC in a tax-favourable state (e.g. Delaware or Wyoming) with residency outside of the US in the upcoming tax year may be beneficial, as it can help protect personal assets and provide tax savings.

Yes, you may have to file state taxes in your original US state but this may vary depending on the specific laws of the state. You should speak with an accountant for more details.

Yes, as a dual EU/US citizen living abroad, you must report your income to both the IRS and any applicable foreign jurisdictions. Depending on where you declare your residence, you may be subject to different taxation rates and could be liable for double taxation. It is important that you consult with a professional tax advisor to ensure compliance with all applicable regulations.

It's recommended to contact a tax advisor familiar with international taxation rules and regulations to determine the best strategies for reducing or eliminating taxes in this situation. Additionally, researching international agreements between the US and the country of residence may provide useful tax benefits applicable to dual citizens.