Dante being a Russian mole is so Season 5. The show has been there/done that. Do you think they’d do it again? I agree he is not who he seems, but who else could he be working for? Simone? And who else? Carrie is treating him and trusting him like he is Quinn, and he clearly is not.
The show already established that there are forces inside the federal government that want Keane out. Most notably because Keane jailed a bunch of them without cause. If he’s a mole, my money is on that – but your point about them already doing a Russian storyline is a good one.