It's all about the height. You can have a million litre tank that's only 600 high and it'll need the same thickness glass as a 100 litre tank 600 high. I'd be happy with 10mm at 650 high but I'd double check with an aquarium safety calculator (i'm too lazy to find one for you).
Plants will be fine with a 100% water change. I'd say just keep the filter wet (full of water) and the substrate wet in buckets and then refill with the hose when you get to the new place.
I'm sure there is a way but I'm not an expert on these things. If it were me I'd either take it apart and cut the sides down to a safer height or I'd only fill the tank to that same height.
Yeah, that's the standard part I was talking about. Could very well be fine but it's not my definition of "extremely well braced". Happy to be proven wrong though.
The price to ship isn't that much from them. They're great if you know how to put them together (there are heaps of sites with explainations) and the lighting is brilliant.
If you don't have an easy source of river sand then silica is a great start. That being said I've got Panda Cories on daltons no.1 sand (which is fairly sharp) and they're fine with it.
Best way to wash sand I've found is to put sand in a bucket up to 1/3 full then put a running hose in and stir it with your hand making sure to not stir so much that the sand washes out but enough that it's all being lifted and washed. Sand should be heavier than the stuff you're trying to wash out.
It depends on the fish you have. Play sand tends to be quite sharp while river sand is smooth. Cories use their barbells to sift the sand constantly and it has been suggested that sharp sand can hurt them. If you don't have any sand sifters you'll be fine with any sand you like - just be prepared to do a lot of washing before putting it in the tank as they often contain a lot of dust / clay etc.
Oh and the Season 1 of The Killing was great, season 2 sucked (they were trying to fill 10 hours of tv time with 2 hours of story) but, season 3 is actually interesting again.