Desler/Desslok is part Iscandarian.The "Batman Can Breathe In Space" scenes in which he talks to Wildstar/Kodai on the deck of his ship involve his cape billowing behind him in a similar manner to Starsha and Sasha's hair. These scenes also occur when he has reason to feel sorrow (after Starsha's death, Flash & Jason's death, and the Argo itself exploding. He also is one of only two Gamilons or Galmans to have blonde hair, whereas the entire known Iscandarian population had blonde hair.
There actually was more than one year before the extinction of mankindThe initial estimate was based on the idea the Gamilans from Pluto would continue bombing Earth at the same rate. With the Gamilas base destroyed, there was a few months more... But, to keep the crew motivated, Okita and Sanada didn't tell them.
The ship isn't the YamatoIt's her sister ship, Musashi. The real Yamato's magazines blew during Operation Heaven One and she now lies completely wrecked and in two pieces, with most her superstructure crushed or scattered. Musashi, however, has not been found and capsized rather than exploding, so it's conceivable it is in rather better nick and could be converted. The discrepancy could be explained by a loss of records during the Gamilan war.
The ship ain't the real Yamato or the MusashiThe spaceship's design is just inspired by the Yamato to serve as a symbol of hope for mankind (and cause the designer was a military history geek).