Send a signed termination letter to the service center assigned to your petition at the address on the NOA1. Reference names of the beneficiary and petitionet and case number.
The Addis Ababa web site has the following link:
https://et.usembassy.gov/visas/immigrant-visas/fiancee/how-to-apply/
Follow the above link and then follow the fiancee visa process link. Look for the required documents section. What is listed will be 95+% of what you need and you can start with that
When the petition is sent abroad, the applicant typically makes their own interview appointment. Timing is dependent on how many appointments are made available and how many other applicants are competing for slots.
Letter of intent and proof of on going relationship is not what the consulate is looking for. They are wanting to know why it took so long for you to pursue an interview and the reasons behind the delay. You will fail if you don't adequately address that issue.
If the refuse to extend and send the petition back to the USA then you will be starting from scratch so it is best you articulate a thoughtful and comprehensive response ASAP.
From your timeline it appears the consulate received the approved petition about 15 months ago. While the petition approval is valid for 4 months the consulate has the ability to extend the petition for up to a year if you keep in touch with them. Did you contact the consulate at all?
Not a lot you can do. The PSA document is the recognized version. Even requesting a new one will result in the same as what you already have.
What are the certain parts that are illegible?
Since the USCIS doesn't assign the consulate you should have contacted NVC immediately upon petition approval. You can try to intercept the petition right now at NVC to get it changed but if you don't then a consulate transfer is going to be plan b.
You might find it helpful to ask this in the Philippines forum for people who are similarly situated. I can't help you with Texas because we did not face the middle name challenge because in MN either party to the marriage can change any or all names so a middle name and last name change for my wife was simple
Might i suggest you visit the DOS website regarding documents
https://travel.state.gov/content/travel/en/us-visas/Visa-Reciprocity-and-Civil-Documents-by-Country/Japan.html