My husband and I aslo bring 阿脾 to Tokyo-Mt.Fuji for 9 days in Oct/Nov last year.
His performance was really unexpectedly......good except he didn't let us shopping (vs Nika didn't let you eat) - later we found that he was scared about sitting on his stroller to go into unfamilar shops.
The night before, I told him we are going on holiday. He doesn't like to sit on his stroller. However, on that morning he wake up early and after dressed, he's willing to sit on the stroller.
For the whole journey, he ate a lot. He also cried 2-3 times everyday when he's sleepy. We just gave him some biscuits or hold him.
He only cried in the last hour on the return flight as he's really tired.
We're going to Taipei in end March and hoping to have a better holiday.
Don't give up. Try to bring Nika to somewhere with shorter flight time e.g. Taipei just 1 hour and have an enjoyable holiday in the near future.