Calculate shipping before discounts

Hi,

Before coupons it's possible.
If you turn off the use virtual product price setting of the shipping methods, the products without weight and the coupons won't be taken into account for the price restrictions.
However, the discounts are part of the products price and thus part of the cart total. It's not possible to ignore them in the shipping methods restrictions.
That would require developing a custom manual shipping plugin which would handle the restriction calculations itself the way you want. While that's possible, it's a lot more involved and will require a skilled developer to help you.