I feel like Reload Speed and Clip Size are the only stats that matter. Fire Rate and Arrow Damage seem to do nothing in terms of getting me farther in a run. Stats that might increase a run length could be Heel Maximum HP, and Heel HP Regen rate.
I've implemented max HP upgrade as promissed.
https://sshulin.itch.io/achilles-vs-turtles/devlog/274045/v-110-max-hp
Added HP regeneration too. It works pretty well! Thanks again for the idea
https://sshulin.itch.io/achilles-vs-turtles/devlog/274730/v-120-hp-regen-new-upgrades-layout