“Tiering” Referral Rates

I read https://www.itthinx.com/documentation/affiliates/affiliate-program-management/managing-affiliates/editing-an-affiliate/adding-affiliate-attributes/setting-referral-rates-or-commissions

And I searched the forum, and this is the closest solution I found: https://www.itthinx.com/topic/affiliates-pro-different-products-different-commisions/

I don’t want to “tier” via affiliates having sub-affiliates like the Enterprise version does.

Here is what I am trying to do:
Default = 20% commission
If total sales exceed $10,000/month, then 25% commission
If total sales exceed $100,000/month, then 30% commission
If total sales exceed $500,000/month, then 35% commission

Is there an easy way to do this? Am I approaching this the wrong way?

Also, is there a way to switch whether the first or last referral wins? In other words, can I either help or hurt coupon affiliates? Or share it?