I don't know the exact stopping point for each character, sorry. If you've got your affection around 60% then you probably have all the scenes (the exception being one scene with Sora, which is locked behind a dialogue option during conversation).
I've looked into making a gallery, but I'm not really good with coding anything in Ren'Py and couldn't quite figure it out. I know there's some QoL adjustments like a gallery that could be made, but I have to keep things pretty simple to accommodate my limited knowledge.