Your TL is officially in the running for douchebag of the year.
Everything that you are describing sounds like, he got wounded pride and totally retaliated against you for clearly doing what was the right thing for our guests and your store. I bolded the key words/pharses you may want to use in the
discussion.
First, I would go to the ETL-HR or the STL and ask for clarification on why you where coached on putting expired product out for the guest to buy, you understand that TL said it was okay, but then you investigated and found the product not to be up to Target standards and confirmed this with the STL, the nearest LOD, reducing the risk of illness or lawsuit for your store and guest. Yes, 500 dollars is a considerable amount, however, the cost of expired or tainted meat would cost more to the store and targets reputation. You felt that you retaliated against and threatened by the TL during the coaching, so now you no longer feel safe even though you did the right thing for the company/store/guest.
I know it will hard not to call out the douche TL, when talking to either the HR or STL, but its about taking the higher road and trying to reach an understanding, upper management hates when these situations become a nasty verbal fight.