When I did a Kickstarter for a client they didn't allow renderings, yet a week after a bigger brand did exactly that, used only renderings. The "rules" are very loose on KS and the projects that I've backed that failed (7 of them totalling 2000$) where all recommended by KS staff.

Yeah, they basically disclaim any responsibility for ensuring the projects get done. But the TOS are trying to establish that you have a contract with the project and thus should have some recourse to get your pledge back if they fail to deliver.

As above, that doesn't work all that well for small sums, but I think it doesn't encourage a free for all either.

Have any that you backed succeeded?

Of course, many, about 10 of them. The most prominent being Oculus Rift and RigidBot (Though RigidBot wen't bankrupt due to severely underestimating shipment costs)

Not really, since that section places no time limit on when things have to happen, they are completely unenforceable. And even if they were, it's beyond the means of most people to actually go to court over the price they paid. IMHO the only purpose that section serves is to deceive potential backers into thinking they have some legal recourse.