AbleCommerce Shopping Cart Software

I'm using Ablecommerce 7.0.4
I'm trying to setup a coupon for scenario where if customer buy $20 or more, then they get item x free. the price of item x is $20 as well.
I see that ablecommerce lack of flexibility with coupons which is very disappointing.

I figured If I use Order coupon with minimum purchase of $20 and use product rule - "valid only with selected products", then choose item x, and then this would allow me to offer $20 discount on subtotal if item x is in cart and $20 or more is purchased.

So, my coupon setting is: Discount Amount: $20, Max Value: $20, Min Purchase: $20 and the product rule i explained above.

But its not working... well it works but coupon gets applied even if other items subtotal is less than $20.

I thought may be I need to make Min Purchase $40. But then even if I add $25 or $30 item in cart, the coupon won't work and gives error that "the coupon you have entered requires minimum purchase of $40" and subtotal is well of $40. Even if I change Min Purchase of $20.01, I get the same error.

Please advice where I'm wrong and what can i do to make it work.

Never mind, I found the answer with bit more troubleshooting:

You have to exclude the Item X in product rule and keep Min Purchase at $20

Thanks

FYI the coupon gets applied even if the "free" item is not in cart.
So, you really have to make sure that customer adds the item in cart otherwise, you are going to have some major issues..