Use storekit to add balance?

I'm a new Swift developer. I'm using Xcode 10.1 and Swift 4.2.

I'm developing an app that shows the user his $USD balance and allows him to use that balance for various purposes within the app. The user can add $USD to the balance - ideally through an in-app purchase. The balance is maintained on my server and decremented as the user uses the app in ways that spend that balance.

I have a few questions:

1) should I use a consumable IAP product type for purchases of a $5 increment or $10 increment to the balance? Do I have to notify Apple when it is consumed? It will be consumed immediately as I add that amount to the balance on my server for use in the app.

2) does Apple take 30% of the amount added (for a $5 increment, Apple takes $1.50)? Is that just for the first year?

3) since the balance can be used immediately, does Apple have fraud filters to prevent someone from using stolen credit card info to make a purchase and then using it immediately for services that actually have a cost to provide? I have been burned with online sales, even though we had professional fraud filters. We still had to eat the chargebacks. That's why I would be willing to pay Apple a precentage to prevent the fraud.

4) if I add paypal to the app as well, does Apple take a percentage of purchases made through paypal?

I'm sorry for the very simple, perhaps naive questions. But I really need to know this information and the Apple documentation is not that specific. Thank you.