Now, that is one wild video.

It appears to be an "ordinary" road bike, in this case Colnago, but custom built to be extremely lightweight, but also durable. Following the video links, there were obviously a lot of crashes, perhaps a crash on EVERY scene. I wouldn't be surprised if they went through several sets of wheels, and probably a few other broken components too. Oh, at least for the first film, 1 set of wheels, and only a few scratches on the bike.

And, unfortunately, one broken back, leaving Martyn Ashton permanently paralyzed, and no longer riding a stunt bike.

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Sorry the Trek didn't pan out. Hopefully the seller was willing to take it back. Having a shop look at the bike isn't a bad idea. Many "roadies" here in the USA, especially those buying older and used bikes do most of their own maintenance. But the older the bike, the more you should be willing to do yourself.

The Jamis Endura and Trek 8.3 DS are very different bikes, and good for their own situations. Either can be used as a commuter/errand bike, and it depends a bit on the rider preferences. The Endura has a good spoke count which is in favor of your plans of using it with rough terrain. Make sure you have a lot of air pressure in the tires. But, if you're planning on a lot of jumping, perhaps tend towards the Hybrid or a Cyclocross specific bike.

There is something to say about a really light $4000 or $5000 bike, but you're not in the fully custom carbon fiber bike market at this time.