The main issues you're going to have are the following:
1. Ultimately, it is you who decides what is balanced and what is not. At what point is reaching level 40 acceptable?
2. How much power do Level Ups actually grant to the player? Reaching Level 99 at the halfway point of the game might not mean much if the vast majority of your stats come from equipment.
3. Balancing XP gain depends largely upon knowing about how many fights to the next level, about how many fights per dungeon a player is likely to have, about how many fights a player is likely to have on the way to the next town... etcetera.
You'll need to make a decision on these things or do some test playing for yourself.
The last RPG Maker game I played used what amounted to the FFX "Sphere Grid", where you would gain an item to use on level up tiles, and gain power that way. It quickly became obvious that this had never been playtested since I was routinely "maxed out" before the next section opened up (it gradually opened up as the story progressed). I was basically steamrolling the entire game. I had spent very little time actually "grinding levels" except at the beginning of the game, and it had snowballed after that point.
So, I would spend 2 or more hours unable to progress in the Level Up Tiles, and then once it opened up, I'd had a ton of those items stockpiled, that I'd max out the next set of Level Up Tiles the moment they'd opened up.
With that in mind, you should largely be deciding your XP values on enemies a bit more in advance. I'm not sure what your values are representative of. They seem completely arbitrary to me. Why is one worth 125 XP while another is worth 660 XP? Why is your XP scaled this way? Any particular reason?
I'd suggest going into game with some goals.
For example: Each dungeon grants each player 2 or 3 levels by the time they end it, if they have not spent time grinding.
You don't have to use that example, but you should be setting up goals like that as you design a game. Then, running playtests to ensure that goal is met. Check enemy appearance probability. Check amount of fights in each area.
Largely, this is what I've done. The player will get, on average, 5-7 XP per fight in this first dungeon. To get to Level 2, it takes 45 XP (the most the engine would let me have). This is 7-9 battles to get to Level 2. On average, the player will hit about 25-35 fights in my first dungeon, not including the boss monster. This means, they'll likely leave it somewhere around Level 3 or 4.
This is some information you should have about your own game. How much XP will they gain, on average, in an area if they complete it? How long does it take to complete it? How many levels do they gain as a result?
I think these are questions you could only solve yourself.
Though, you could just get people to playtest for you if you want a more accurate read on how much XP they're getting per location and how many levels they're gaining on average.
I don't think it'll be useful to have other people try to fix your XP curve for you.
