Some answers, Simon
1. Is the 6-cord arrangement standard
Three sets of risers from each side is the most common arrangement these days - older gliders used four sets, but control of the shape of the wing has improved with time. Many high performance (and high aspect ratio) wings now use only two sets for decreased drag, but there are other issues with only two sets that mean you really need to be doing a few hundred hours a year to be able to handle them.2. Is there a difference between and forward- and reverse-takeoff (I liked the last example best)
A reverse launch is one where you start facing the wing, back to the slope and the wind. You bring the wing up into the wind, and you can see that all the lines are clear more easily, and also that the wing is coming up without any nasties waiting to bite you. With insufficient or no wind a forward launch is your only option and there are a number of disadvantages: you can't see the wing until it is overhead and it's easy to let the wing overfly you; alternatively, it comes up with a problem on one side or the other, or with a knot that you didn't find... I much prefer the reverse launch but do a forward launch if I'm towing (unless the wind is too high!) or in nil-wind conditions.
My favourite launch was the second reverse launch at about 2:20 - the wing got walloped by turbulence and suffered a frontal collapse but I managed to catch it and continue the launch 
3. Is the principle of control similar to say, the two-cord stunt kite
Similar - though I cause amusement whenever I fly a kite since I hold the controls in the 'wrong' hands - my reflects are build around the paraglider and I don't want to upset them. A kite, though, is usually flown in the power band - full drag - while that's the last thing you want with a wing: mine is thirty square meters. They're both flex wings, but the glider offers much finer control of the brake and the shape of the wing. So I can go up in suitably lift at ten meters a second (six meters is common in the mountains) and pull four g in a tight turn though I try and keep it under a couple of g...4. How long does it take to set up
A full setup, coming to a new site for the first time, might take a couple of hours, because you're checking local weather conditions and watching the locals to see what they're doing (and particularly, not doing), but if you know the site, the first flight of the day might take half an hour to check the wing and lines, reserve, harness (daily checks) and get your flight suit and helmet and gloves on etc. A subsequent flight on the same day might be as little as five minutes even if the wing is packed back in its bag. Then again, if you're on a tow day, you can land at the takeoff point, spread the wing, hook the line on, and be ready to go in thirty seconds...5. How long was this flight down, and the return to starting point
On a mountain in the last year, I haven't had a flight of less than half an hour except for the last two shown on the Passy video, which were non-thermal sled rides aka top-to-bottom - about fifteen minutes to drop 700m from takeoff to landing field. The first of those top-to-bottoms was so stable in the air I flew hands off from take-off to arriving over the landing field, steering just by weight shifting.
Longest flight at Passy was an hour and three quarters, cruising all along the ridge (10km or so) at about 2400m; longest from Samoens was an hour or so. In Spain I've had flights of a couple of hours up to 2700m from Ager, just as long but not as high at Algodonales. Getting back up the hill at Passy was a half-hour drive. It's at 1500 metres so already higher than Ben Nevis.6. Which parts of the body take the most load
The most obvious is the upper arms. In anything other than still air, you need your hands on the controls and you need to maintain a pressure downwards of a couple of pounds, compensating for changes in the shape of the wing. Since your arms weigh rather more than two pounds, you're effectively holding your arms up for quite some time; in the army this would be called a 'stress position'. You can change the position of your arms by taking or releasing a loop of brake line around your hand which moves the hand up or down by a foot or so, which helps. If you can get some time with no control inputs needed or expected (see above) then you can get some relief that way.
Second is the belly muscles: if you're working a ridge in ridge lift or thermal, you do a lot of weight shifting as well as brake control.Try putting all your weight while sitting onto one side then the other, and do that for an hour or two... planking is easy
Finally: the brain. This is not an adrenaline sport, it's a continuous mental exercise as difficult as doing the Times crossword or playing chess blindfold. You are continually trying to work out what the wind is doing, what it is likely to be doing in ten minutes, watching for thunderclouds forming, observing other pilots, trying to remember the site rules, any prohibited areas, air traffic control areas, and generally trying to stay up for as long as possible - or on occasion, trying to get down... https://www.youtube.com/watch?v=-VUofPgixWk
Those guys made a fundamental mistake: they got to a new site desperate to fly, and failed to observe a building storm. Cloud suck - massive lift - at the end of the valley can lead to seriously strong wing further down the valley...I guess a "flight" is as long as you can make it, as well as a question of stamina
I saw last month that the new world distance record now stands at 660km!As a comparison - some people making fairly horrible attempts at takeoff...
https://www.youtube.com/watch?v=k0Cmh8-xy0A (to be fair, selected from a lot of much more successful attempts!
Neil
and nice camera work too.
