SIDSTAR:
I have no doubt in my mind that the 737 is an easier aircraft for pilots to convert to and not just because it doesn't have the advanced design of the 320. It is simply more intuitive and therefore easier.
You really need a second "In my opinion" or words to that effect in your second sentence, otherwise it comes across that you think you are the definitive guru on man/machine interfaces. Having said that, this does not make your opinion or experience any less valid in this discussion, but it'd be nice to acknowledge that other people's opinions may differ.
Anyhoo, I'll have a go at these with what I've understood from my participation here:
1. Why would any pilot leave the Thrust lever at CLB
This could be anything from a fundamental misunderstanding of human psychology in the design of the interface to a simple mistake by the pilots concerned.
2. Why does the availability of autobrake depend on spoilers
At a guess I'd say this is because without spoilers the aircraft will become considerably harder to stop and the designers considered it better in that situation to promote a go-around and a second attempt to land or a diversion.
3. Why was this aircraft designed in such a manner that if the automatic deployment of spoilers fails for whatever reason, manual spoiler control is not available to the pilot when he most needs it - on the landing roll in limiting conditions.
Again, guessing here, but I think it was to prevent inadvertent manual spoiler deployment in flight, the cause of several accidents and write-offs in older aircraft.
I know that there will always be a desire in many pilots to be as directly connected to the metal as possible, and that is what you're talking about in your post, and the Brazilian pilot in China was saying in his. As a programmer I like to occasionally go back to 'hitting the metal' and do some hardcore bit-flipping because it gives a rush that you don't get so much with with modern languages and their in-built safeguards.
But those inbuilt safeguards are there to make us more productive and make the other aspects of our jobs easier, just as the intention was with the A320 cockpit interface. It's hard to say whether pilot consternation at a computer-controlled aircraft was caused by a genuine concern for safety, or a concern that the presence of flight envelope protection might lead to 'de-skilling' of their jobs. In all likelihood it was a combination of the two.
But of the few airline pilots I've met in my time, there are some that find the A320 interface as intuitive as the more classic cockpit design, in some cases even more so. And there are some that feel the same way you do. Either way it's horses for courses and we should try to keep everything as safe as possible - it's always a trade-off really.