Yes, they are available to order from the website mentioned on the video.
The g could last a year or more, the b six months or so, the e anything from five minutes to five months. A common cause of broken first strings is people tuning them to 440 when they were not designed to do so (thankfully these strings are), or having rough spots on the contact points with the guitar: nut, bridge, bridge holes, and frets. Also, fingernails can shorten the life of the string IF they are not well polished before each session. You can hear the sound difference quite clearly. If you can't, then don't waste your money. They do sustain. I haven't noticed a problem in that regard. Yes, they feel different, a little rougher, which is a good thing if you play with more flesh than nail.
People played with gut for millennia. During that time, quality varied. There were international centres of string making, and good-quality strings were much in demand by those who could afford them.
I ignore qualitative arguments about which is best, gut or nylon. The fact is that gut strings have played a HUGE part in the history of the guitar, all of the centuries up until mid way through the 20th. Gut and nylon are both good, but sound different, and neither type will suit everyone. But to me, playing good-quality gut strings on a guitar copied from Torres, Manuel Ramirez, and Santos, with the flesh of the fingertips, is as near to nirvana as I'm every likely to get. Your mileage may vary, as people on Internet fora are wont to say.