What options do I have if my I-485 has been pending for 10 months?

You can continue to make inquiries every 30 days or so. All cases are taking much longer to process than they have in the past.

I would suggest you follow up with the Congressman. You should receive feedback from his office. If you need to travel or work, consider applying for advance parole and EAD.

This is not unusual. I-485s may take 12-14 months. You should wait until you receive a response from the Congressman. You may also want to schedule an InfoPass appointment at your local USCIS field office.

10 months is not overdue; these applications routinely take longer than 10 months.

Put in a Service Request through the Customer Service line, follow up with that Service Request to the Service Center after 21 days and then follow that up with an email to Headquarters after 15 days. Contact the Ombudsman thereafter. Your attorney should know these email addresses.

The application is still pending as you have not received any decision to the contrary. Also, please note that there is no expedited processing option for I-485.

This could be a frustrating matter; there are very few options except to make periodic follow-ups and reminders with the hope that the case is not lost. You could, as you have done, get a member of Congress to make an inquiry but that often only makes sure that the case is not lost and the Congressman may receive a very similar response that the case is under "extended review." An extended review could mean anything; it could be for a security matter or something else. Unfortunately, they will not tell you what that matter is. Finally, if you have no choice, you can always retain legal counsel to file a writ of mandamus in Federal Court on your behalf.

All you can do is wait. They are taking 14-16 months to rule on EB-5 cases.

You have the option to do an in-person inquiry at the USCIS district office nearest to your residence through an InfoPass appointment. They usually have access to your file (instead of a computer database) and may be able to give you more information. 10+ months is not unusual for I-485 processing (depending also on your jurisdiction), but may be worth an InfoPass inquiry.