I don’t know how much flour you’d need but you should definitely increase the other ingredients by the same proportion as the flour. If you have a recipe you like for an M inch pizza and you want an N inch pizza you should be able to scale all the ingredients up proportionately by calculating the area of an M inch circle and an N inch circle. But bear in mind that rolling out a ginormous pizza and moving it around is difficult (I’d definitely use a pan rather than trying to get an 18” or larger pizza to slide off of a peel onto a stone). And make sure your oven is big enough.
I’ve been using One Note. I had the same issues you had with paper and recipe cards and I happened to be using MS office a lot in general. It’s handy since I can use it from my phone or laptop and can share with family. I copy internet recipes to One Note since they can be available offline and since sometimes recipes on random sites disappear.
Converting to something I can self host would be cool.
I don’t think I’d ever use meal planning and shopping list features. It would be nice to have an easy way to generate nutrition info for my invented or modified recipes.
Oh, and I do like flipping through cookbooks for ideas. When I see something I like in a cookbook, I use my phone to scan it into One Note.
It can be a little awkward flipping between recipes when I’m making multiple things from recipes at the same time. My setup is good enough but not great