I think we need to step back from the tech areas for a short while, we need to look at the process.
1: do we need to ensure that pull down is achieved with 2.5hrs.
2: Which cabinet is used the most.
3: Does Chef, want/can make possible major changes. (what can be completed without destroying the cabinets)
4; What level of controllabilty is required.

From my point of view, the system is presently running short of refrigerant, causing high superheat, and then the SH is made even worse by the Suction/liquid line heat exchanger.