The pooling under your pad is a classic rookie move, I did the same thing once. I angle the tarp so one corner is lower than the others, water runs off that point instead of gathering in the middle. Also, bury your groundsheet edges under a few rocks or fold them up, that stops water from sneaking underneath. Did you have a drip line tied under the ridgeline too?

Hold off on blaming the pitch, that heat was the real problem here.

Did you actually weigh out your beans after the drift happened, or did you catch it by taste alone? Curious because gas station scales are already sus, but 3 grams off is straight up sabotage for a 1:15 ratio. My old cheap one would read fine for a week then suddenly add like 2 grams out of nowhere, drove me nuts.