This doesn't make a lot of sense. You're paying for a wedding, and you thought you had $9,000 on you. This is apparently a lot of money to you. But, your wife slipped you $3,000 extra "as a surprise" which put you over the $10,000 declaration threshold. Your dad also decided to throw in an extra $3,000 at the last minute, so you're up to $15k now - or was it $16k (9+3+3=?).
So, you've been working hard - in a foreign country since you were on an inbound international flight when you apparently got secondaried and searched by CBP, who found your wad of dollars. Now, if you're working hard and saving for three years - but apparently also borrowing money for the wedding "at an extremely high interest rate" - how exactly were you getting paid in US dollars? If you're saving for three years and borrowing money to make the initial $9,000, how did your wife AND father suddenly come up with another $6,000 to give you at the last minute?
So you're carrying this pretty big wad of bills with you - dollars somehow saved, given and borrowed in another country that presumably has it's own currency (unless you're coming in from Panama or Ecuador) - and you never do this so you don't know the rules. Did you by any chance read your US Customs form that you were either given at your original airport or on the plane, that you filled out and signed, that very clearly asks in Line 13:
"I am (We are) carrying currency or monetary instruments over $10,000 US or foreign equivalent (see definition of monetary instruments on reverse)"
with a "Yes" and a "No" box beside it? Did you read that and checked the "No" box, even though you knew you had at least $12,000 (or maybe $13,000 depending on your math)?
Your story doesn't add up. Why didn't you answer Line 13 correctly and put down the amount you thought you were bringing - which was clearly over the declaration threshold? Why were you sent to secondary inspection in the first place? Your math seems off and a lot of your story on how you came about the money seems very strange.