Hi SarahJane Welcome to the tree, and to the delights of motherhood
Looks like you've got a nice little stash there, some great choices. Some andswers to your questions
1. When I fold the poppers I point the folded bit in and down. So you would use the bottom poppers to snap into the top row then fold the flap bit down.
2. 3 tablespoons sounds like a lot to me, for each wee. I'd honestly think it was a lot less than that. But who knows! Anyway couple of things, have you prepped your nappies? That is washing them 3 or 4 times and drying inbetween? You need to do that before using to get the absorbancy going.
But in answer to needing to change the wrap. No you don't, as long as its just damp on the inside then its fine to re-use. If its got poop on or in the VERY VERY unlikely event that it gets totally sodden (if you left a baby in one nappy for a day kind of sodden) then you would change it. But with a newborn you'll probably change before or after every feed so some people will even just leave a newborn in the fitted nappy without a wrap because the outside never gets totally wet.
3. They all seem bulky to start with. You are used to seeing disposables which are super thin, but after a few days of holding your little one with a great big fat bum you'll think its odd when (or if) they wear a disposable.
hope this helps