I'm excited to look into this deeper.

Have you experimented with stemming for the full text search?

I've built (much simpler query DSLs) in nodejs & golang. Adding stemming and also boosting rare words (TF-IDF stands for “Term Frequency — Inverse Document Frequency”) helped my use-case for recalling favorite tweets

I see that the original JS version has TF-IDF - so perhaps your port does as well