You never know if you had copy someone or not, there tons of systems stories out there, so the chance that your look line another is huge.
Different reader like different system, a lot complain when the system is alive, some complain when there no origin of the system by the end of the story, it really depend. You can come with a living system that annoy the MC and readers will like it if doing well, or it just become annoying for everyone.
For the stat use Math, its really good to keep tract on those number. Joke aside, use a file to write down the number on each chapter, even if you don't show the stat, just so you can follow the advance of the stat.
For levels, it depend how you want your story to progress and the limit of the levels you set, like level max is 1000, then you need to fix how many monster of the same level you need to kill to level up (monster or quest or anything that help level up in your story), and then you can use a percentage, you decrease it if the level of the monster are lower than your character, and you increase it if the level of the monster is higher. Here again the percentage depend on you.
For spell points, it's the same, it depend on you, how you want your spell to progress and how fast you get those spell point. Is it by doing quest? Or each 5 level maybe?