Next isn't done for yet, we have had some members leave the project (most notably our ASM hackers and our lead developer) but a few of us are going to try and salvage the mod, though it will be aiming lower and won't have ASM hacks anymore (no new power ups or enemies).
Thank you so much for reporting these bugs! We will work to fix them! (BTW the images you uploaded aren't showing up properly, I recommend uploading to imgur.com and just copying the image urls from there)
You will download a plugin and the mod files, put them on your sd, and then everytime you want to run the mod, you have to run ntr cfw, close and then launch NSMB2. It won't enable installing a CIA of just the romhack changes afaik.
Yes, a layeredFS version of the halloween special, when the full mod is done we'll have a layeredFS version of that too, (though that won't be for a while).
We might do an xmas one next year. As for the custom power up, we are hopefully having at least 1, I'm not going to say what, so as to not ruin the surprise. That's just one of the cool things we have planned :)