Yes. The app is completely free to use without limits.
Yes, you can setup your affiliate portal under your own domain or subdomain. This is a bit technical process, so we recommend getting in touch with our support team to help you along the way. See the section on setting up custom domain for more details
You need to advertise your affiliate program on your social media (facebook page, instagram, twitter etc.) and your store's homepage (by means of a footer/header menu link). Let your customers/site visitors know that you have a affiliate program and they will come
You can set cookie duration by in Settings -> General Settings -> Scroll down to cookie duration
Commissions are calculated on product price only. Shipping/Taxes/Coupon Discounts are excluded from calculation. Why ?
This is industry standard practice
Affiliates get what they see (i.e. on your shop they see a $100 article and if you are offering 10% commission on its sale, they are sure they'll get $10 for its referral). This creates a predictable and transparent affiliate program.
Shipping/Taxes/Coupon Discounts are variable depending on country/state/customer location etc, hence incorporating this would incur a great accounting overhead