Ok so I haven't played the mod yet but I still wanna quickly say something before I see what the heck this is
First: You aren't the first to make an updated/"better" version of Cave Story. Cave Story X, Cave Story NG+, list goes on. The thing is, you can actually make a decent updated version of Cave Story. It's just that a lot of people here have played through Cave Story like 100 times or something, and playing through it again with slight changes is probably not what they want.
Second: Oh my god thank you for making it possible to trade back the Polar Star from Curly, I still remember my first attempt at a best ending run and I accidentally traded the Polar Star while skipping textboxes and I didn't save since the middle of Grasstown
And finally: You can easily fix the out of textbox bug by making sure each of your lines don't go out of the textbox and hitting enter before it does.
I'll go check this mod out soon. Since it's only in super early beta I doubt there's a lot of changes so far.
Also one more comment: yeah, nobody's interested in your mod if there isn't any screenshots.
EDIT: Oh well nevermind then, guess I'm not looking at the mod. Got too distracted about side projects... oof