1. it's an auction. By listing it, you agreed to accept the winning bid amount

2. if you're not prepared to wait 2 weeks for payment, cancel the sale - but as for postage, you advertise postage at $9.15 so you have to provide it for that price

3. yes

4. how do you know what payment method the buyer used? With eBay managed payments, I just get a message that the buyer has paid. There is no notification of which payment option they used