i am sorry that you encountered such difficulties :S
you gave some good points for improvement, and i will pass them to consider for future chapters. i am not sure how many of them can be done on chapters 2 and 3 since changes in previous chapters tend to cause new bugs. from chapter 4 a preparing for combat screen is added which let you choose if you want to use potions and war supplies in the combat.
a short guide was posted on discord with basic explanations on chapter2 new features when it just came out, i see that it is not available here with the chapter itself so i will ask to add it.
in the game itself, in chapter2 anders conversations explain about the combat system. i agree that its easy to pass on, that is why there is section on combat in the short guide. i think that since you encountered a fitness bug you had the first battles too easy and missed the oportunity to figure out a strategy by yourself in the trainings. stuff like the number of medkits for the boss of chapter3 is just something players thought about on their own. you may not really need that much medkits, but its a general recommendation to players who find this battle hard since it covers most/all the fight rounds.
please consider joining the discord since its easier to have a conversation there, and you can write your suggestions or about bugs you encountered in the related channels.