Sorry about the belt.
I'm new to Kymco's - but familiar with CVT's and the promises of better accelleration due to lighter weights or different ramps. You get better accelleration by running the engine at a higher rpm at the same speed. That means you are going to be running hotter. It also means that you are putting more torque on parts, hence reliability is going to go down.
I've used a Malossi belt, but I used it with a Malossi Variator. Because I've seen differences in the ramp angles / belt shapes - I'll only use belts and variators that are the same brand.
I'm also familiar with complaints of DR P's causing belt problems on Yamaha Zuma's.
Lighter weights cause the engine (and the belt) to run at a higher RPM for the same speed - increasing the applied force, temperature and wear. Weights that are too light may not push the ramp out properly which results in good acceleration but a drop in top speed - they can also cause a wobble which dramatically increases wear.
A new belt, new weights, new variator or new rear pulley all need to be broken in. Just like chains and sprockets on a motorcycle - I'd also replace them all together.
After the upgrade - what changes did you notice? Did your top speed go down, any new noises or vibrations? You were cruising at a steady 6000 rpm - was this for a long time? Had you broken in the new parts before starting this 3 day trip? What rpm do you run at 70mph now? After the upgrade but before the failure - did the bike not roll as freely as before (when not running)? If the nut that holds the clutch on comes loose - then it can let the pads on the outside radius of the bell causing a drag and damage.
The way that I look at it - is that the manufacturer picked a setup that was a compromise between reliability, fuel economy, and acceleration properties. If that weight roller, ramp shape, spring strength... were reliable - then they would have used it.