Roller-Coaster
Factoring in his Aether Vitality, Body Vitality and the 8-fold multiplier from his Myrtharian Body, Jake's metabolism was about 3560 times faster than that of a normal sedentary human, even taking into account the local Aether density of over 60.
In other words, he could recover from a serious injury requiring three months of recovery time in only half an hour, while he could recover from an open fracture in only fifteen minutes. Even by the standard of a Fourth-Ordeal Evolver, that was a terrifying number.
This did not include his Real Constitution, which when taking into account his various stats and abilities was estimated to be about 4089 times that of a normal human. In addition to his stats, this included other specifics such as the fact that as a Myrtharian, he had digested many metals and minerals as a snack, his cells themselves containing a significant amount of Silver Alloy.