A Couple of Questions (SPOILERS)

1. Who texted Lucas that he knew where Piotr was?

2. Was the dead guy in the barn Pyotr or his large brother?

3. Where were the good diamonds?

4. Was Lucas reaching Gabby's voicemail symbolic that she had left him or was about to?

I'm willing to accept that Boris could find Lucas in Siberia, though it's a stretch he'd find him that fast.

My theory: Katya's brother texted Lucas that the fat brother had talked about Pyotr. They went to talk to biggie, but he's the dead one, killed by Pyotr. Pyotr kept the good diamonds to sell, maybe to Vincent. He, after all, helped the FSB guys by giving them the fake diamonds to screw Boris out of the money. Most of that money, if not all, went to the FSB guys. They probably wanted to even a past score with Boris where he had screwed them, or beat them to some other lucrative deal.

Am I over-thinking this?