Remote marriage and social security survivor benefits

I'm not sure this is the best forum to ask, but I'll try.

I'm a U.S. citizen living in Japan. I'm a permanent resident here. I live with my same sex partner of 20 years. While eligible for U.S. social security I have not started taking retirement benefits. I will in a few years.

I would  like to ensure that my partner receives social security survivor benefits when I eventually pass away. He has never been to the U.S. And we cannot marry in Japan.

After checking all over the place, including reading social security info, it seems that this is possible:

1. I can remotely marry my partner in the state of Utah which has become very open about allowing this over the last few years.
2. While most foreign spouses of U.S. citizen must have resided in the U.S. for 5 years to become eligible for survivor benefits, there are a handful of exceptions, including Japan (see https://secure.ssa.gov/poms.nsf/lnx/0302610010).

So I think I can go through a remote marriage in Utah and as long as we are married at least 9 months my partner will be eligible for full survivor benefits when I eventually pass on.

Is that right? Any way to confirm for sure?

Thanks.