Easier with Android. Apple requires many hurdles, at least for US. You'll also then have to revenue share.
Depends on your audience on whether this will actually be worth the investment. Being on the app store doesn't necessarily make you visible anyhow. It's just easier to install for apple users.
True enough. However, you also need to consider that customers are much more likely to hand their card number over to Apple than to some random website they've never heard of before. In fact, Apple probably already has it.
70% of something is more than 100% of nothing (especially when the product is software or something else that has a marginal cost of production of essentially zero).
Depends on your audience on whether this will actually be worth the investment. Being on the app store doesn't necessarily make you visible anyhow. It's just easier to install for apple users.