To address the issue of the thrust lever position. They were in exactly the position the flightcrew expected them to be for most of the approach until the speed started to decay.
The aircraft intercepted the localiser beyond the normal descent point and appears to have been hot and high by several hundred feet initially. As they got a gear warning they were obviously gear up. They then rushed to configure the aircraft as quickly as possible. Anyone who flies the NG will know that from above the glide, with this kind of wind, this takes time unless you bust limits.
You can only complete the landing checklist when fully configured. As this occured very late they appear to have been focussed on this and probably looking out for the runway, rather than registering that the autothrottle was not working as expected. This might explain why the 'pilot flying' left the automatics in so long. Had he been flying manually it is extremely unlikely that things would have deteriorated to the extent they did.
When they finally realised much too late what was happening they were too low to recover. Once again the fundamental error was not being stabilised early enough.
A more experienced 737 'pilot flying' would I believe have had the gear down and been busy configuring before the localiser intercept.
This is a classic case of swiss cheese holes lining up. Not being stabilised, combined with a minor technical problem and training / command gradient issues resulted in catastrophic failure.