Looking for proof of grandfather's name change

My grandfather is 90 years old. He moved a few years ago and lost his documents in the process. I have been trying to get proof of his name change and keep coming up dry. Below is a timeline of what I've attempted (Note: I redacted personal information but please reach out if you think you can help and need this information): 

[Redacted] was born in Riga, Latvia in 1933. He left with his mother and brother to escape the war
and arrived in the United States from Latvia in 1950. He moved to North Dakota immediately and was
using his birth name, [Redacted]. He was told changing his name to something more “American”
was a five-year process so he attended high school under the name [Redacted].
When he graduated from high school, there was a draft and the army said when he could join after
naturalization or they could take him immediately and get naturalized in the army, which they claimed
would fast track his naturalization. This process was not fast-tracked.

In 1955, his five years were up. He was in Hot Springs, AK working at the army hospital as a medical
specialist. They told him he had to go to court to attend a class to become citizen. When he did that the
instructor suggested that if he wanted to “Americanize” his name the courthouse could do it because
they would do it for free. Naturalization papers were issued in Fort Smith, AR with name the change. At
this point, he was married to his wife (a US citizen) who was still [Redacted] after he became
[Redacted]. They had to go to the church so she could change her last name to [Redacted].
Attempts to get proof of name change:
North Dakota
- Recorder’s office - Stutsman, ND
o They do not house the name change documents
- State Archives/historical society – North Dakota
o Said they only have records UP TO ~1919
- District Court /Clerk of Courts – Stutsman, ND

- Sebastian county clerk - Fort Smith, AR
o Couldn’t help, transferred to Circuit Clerk
- Circuit Clerk - Fort Smith, AR
o Couldn’t help, transferred to Records
- Records Office - Fort Smith, AR
o 8/4 emailed FOIA
o Response they would look but aren’t obligated to respond to FOIA

o Couldn’t find anything, suggested reaching out to Crawford County
- Crawford County Records Office - Crawford County, AR
o She said to try VA
- Crawford County VA - Crawford County, AR
o Called VA 
o Suggested ordering DD214
- Sebastian county district court – Sebastian County, AR
o Transferred me to Fort Smith district court 
- Fayetville District Court – Fayetville, AR
o They only ceremony

Started process with USCIS in August 2022. This has been "actively reviewed" since then. He did an in person interview to prove he was who he claimed to be, we've supported any documents we DO have, etc. Nothing has helped. I checked NARA today and found a record for his mother's naturalization but not his