Opt-in rate depends on your landing page and your offer. As nobody can control over people's activity I can't guarantee high opt-in rate.
Do you accept order with direct sale page?
Solo ad works better if you use a simple opt-in form at entrance. To get sales main task is proper follow up to convert subscribers to customers. I discourage using direct sale page.
What is the tier 1 percentage on your traffic?
I always provide 95%-100% T1 traffic.
What is the Tier 1 (T1) percentage of your list and from what countries?
I send traffic from over T1 95% + (US, CA, UK, NZ, AU) and I also have an option to order only T1 100% traffic.
Do you over-deliver? If so, how much?
Yes I always over-deliver 10% clicks on the total amount of the order. If you order 100 clicks, you will receive 110 clicks (10% clicks free).