Graeme realizes Sam needed to prove himself capable and he seemed quite satisfied with his skill.
Despite Graeme's words, Sam feels his discomfort during his first taste of bartle was a sign of weakness when it was not.
If circumstances were different...? How might circumstances change? As Sam said, he is a man. He can make his own choices.
The mercs first fatal error was not gathering intel while onboard the recovery ship. It was common knowledge the sub was severely crippled. Instead they isolated themselves. The second was shooting the XO. Thee was buying blindly into Andrew being Miller/Reza.
I don't see how the mercs can see this as a survivable scenario. They can't move or hide and both the Richmond or Russian sub can easily sink them.
If Andrew can separate one of the mercs and get a gun, he'll have a chance to retake the boat.
Remember both Hugo and Stoker touched the oily substance in the watch mechanism. It's what has linked them together. Stoker's watch is broken, at least partly.
I doresee another coded message from Andrew.
Despite this being bloodless so far, I don't see it ending the same. They are bound to scuttle the boat before leaving.