Really solid write-up on this card. One thing worth adding since you mentioned the tarot correspondence - the Jack of Hearts sitting at position 11 in its suit creates that master number energy you touched on, but there’s more to it. Some older systems describe the number 11 as ‘a man (1) beside God (10)’ which adds a whole spiritual layer to why this card reads the way it does in spreads.
The ‘Christ Card’ association goes deeper than just Pisces symbolism too. The Jack of Hearts is placed at the very center of the spreads in the Destiny Card system, where the lines form a cross - that’s actually where the name comes from. The idea is that this card ‘wins his crown through sacrifice for love’ which explains a lot about why the reversed meaning trends toward martyrdom and emotional immaturity when the energy goes sideways.
I’ve also found when this Jack shows up paired with another Jack in a reading, there’s a specific traditional meaning - a meeting of two young people. Interestingly the second card supposedly ‘does not speak’ in that pairing, so the Jack of Hearts dominates that combo.