A question about ticket transfers

Hello,

I used PayPal G&S to buy a ticket from someone and they showed me the screenshot of having changed the shipping address to mine. However, I have two concerns:

1) In the screenshot of the address change, the button to edit the address was still available. What's to stop them from changing it back?

2) I also noticed that this person had a remaining balance. Now I'm freaking out about if they don't pay the remaining balance and then the ticket never gets sent?

Thank you.