I'm glad to hear you figured them out, I simply misunderstood your problem then. I do think having Sprint on SHIFT is the standard for pretty much every RPG Maker game out there, coupled with most other games with a sprint function, though, and it is clearly listed in the manual. Unfortunately the link did go down, but at least now you can use my link to make sure you've got the basics down!
While you might argue the game suffers from a lack of healing potions, I've had other players complain about them sitting on 100+ excess Tears after the Fire Temple, feeling like they have so many healing items they simply start every fight fully healed. Balancing is difficult, as someone will always think the game is too easy or difficult. I can assura you however that the game has been balanced around player feedback to the extent that I know for a fact no area is (even close to) impossible.
Clearing out an area gives you rewards in itself, as I'm sure you've noticed by now. Yes, you do end up not being able to "grind" Tears, but the game economy was never balanced around grinding, and you can make it through the game while only fighting each fight once, clearing areas as you encounter them.
If you feel like Celia could use more healing, maybe you should invest in a self healing move? You can always look through the manual to plan your skill and stat builds.
Normal mode in Celia's Quest is balanced around being tough, but not impossible to beat, with every build that isn't actively trying to be weak. Hardcore mode is balanced around requiring the player to build incredibly potent skill and stat setups, while Casual mode is much more lenient with player builds in general. Neither of the modes are easy, which is why there's no mode called "Easy".
I understand the game might feel a bit too challenging if you're going into it expecting a usual JRPG-inspired story focused grind-styled RPG, which tends to be the norm as far as I can tell. But that wasn't what I aimed for with Celia's Quest, I wanted something truly challenging without relying on simply cheating the player, but rather forcing the player to really think about what to do next and how to do it, and judging by the responses I'm getting in this forum thread, I feel like I've succeeded in doing just that.