The burden of proof is on you (which is why I said "government treats you as a criminal by default"), and I doubt "it's from a dead exchange's gains" will cut it, even if it's the truth, which is why im worried about cashing out these coins, or coins which I mixed back in the day to text a mixer. Now there aren't clear traces about these coins.
So this thread has been ongoing for quite some time now. What have you learnt and what are you going to do? You seem to be locked into a particular spiral of doom and nothing anyone says is talking you out of it.