I have taken this flight between BKK and VIE a few times. At first I always reserve the Emergency exit seats as a SEN and then if there is enough space I get them to block me a whole row of 4 seats which they usually do without any complaints.

The armrests are moveable at least on the seats that I have used as 'Student First Class' so to say. Not sure which ones your are referring to (what part of eco cabin) that have immoveable armrests. I think they don't disappear between the seat backs all the way but stick out at an 75-80 degree angle maybe. Still not bad when you are lying down.

Food I can echo, it was by far the best Eco food I have eaten on any flight including numerous SQ flights.