GREAT WORK!
Love the fact that's it's an SLK32 as well......
With your runs - is the water/meth off or is it running in combo?
Is the box insulated, I'm guessing so.
So - looking at 10kgs of ice to water (335kJ/kg) say over 120seconds of "need" = approx 30kW or 100,000BTU/hr....

Coolant temp into the charge air cooler would be good - then you could just switch your 3 way from IC to no IC.....and [the temp diff between the 2] x [flow rate] x [cp] being your ambient ingress to the IC.

Going by your AIT in graph 3 it going beow ambient - so no brainer....