You're more than welcome! Now I'm rather curious to know what tools do you use to make this game?
I'd also echo the consideration that you should take a look at those levels. If you change a game mechanic, then I think you're definitely going to have to change the levels, and I personally don't think that being reluctant to change your level design is a good idea at all. In my opinion, you should definitely reconsider your reluctance to change your mechanics and level design. In the process of changing things, you might even find new and more fun ways to use the mechanics you already have or even come out with a whole new concept based off of the changes you made. The possibilities are endless and I'm not a fan of locking myself into having one way to do something. Maybe you don't even need to change the jump at all, maybe you could just make the jumps in the first couple levels less precise and let the player acclimate themselves to how that specific mechanic works before you start throwing pixel perfect jumps at them. Maybe the jump should be half a tile longer or shorter than it is in order to give players a bit more leeway with their jumps in general. I dunno... at this point, I'm just throwing stuff out there to see what sticks.
Level design is my absolute favorite aspect of making games though, so if you want to talk to me about it, then I'd be more than happy to! In a lot of ways, your game has similar movement mechanics to the project I'm currently working on. I make and get rid of levels in my project more often than I change any code at this point... but that's beside the point. Are all of your plans for the levels to be fairly short maps? If so, how many levels are you looking at making for your full game? Do you have plans for boss encounters or anything like that?