Now, by the way, Delaware DOES have some laws concerning usury, too.
CHAPTER 23. INTEREST
But it does look like you have the facts correctly stated relative to South Dakota, Polk.
South Dakota Codified Laws
It may just be that Delaware has such a high rate that it's like they don't have one. I didn't see anything about what the cap was in that link.
Try this from that link:
§ 2301. Legal rate; loans insured by Federal Housing Administration.
(a) Any lender may charge and collect from a borrower interest at any rate agreed upon in writing not in excess of 5% over the Federal Reserve discount rate including any surcharge thereon, and judgments entered after May 13, 1980, shall bear interest at the rate in the contract sued upon. Where there is no expressed contract rate, the legal rate of interest shall be 5% over the Federal Reserve discount rate including any surcharge as of the time from which interest is due; provided, that where the time from which interest is due predates April 18, 1980, the legal rate shall remain as it was at such time.
But that only applies to Delaware chartered banks. I think that's where we get the conflict. Delaware has a tight cap on state-chartered banks, but no cap on federally chartered banks.