I guess I'm not understanding, item 3 on what you provided states Cash discount Section 339.001 prohibits surcharges for paying by credit card, but it does not prohibit discounts for paying by cash, check, debit card, or other methods. A surcharge is an increase from the regular price of a good or service, but a discount is a decrease from the regular price.
What i said was raise all your prices to the 4% and then offer a discount to those paying cash or debit as it allows.
Unless I'm missing something and if I am +1 to Canada