From my point (based on what you know) it basicly goes down to the point if you trust the Cats enough that you leave Belenkiy in their hands. If they are truthfull and return him by midnight next day, you will just get your payment delayed - that is what I tried to put into Falcone's mouth.
If they kill him and the ransom details will be publicized, well ... you'll probably be dead before midnight as well, and you street rep will get a hit for sure.
If the ransom details get publicized without you having Belenkiy ready to prove them false, you'll get the street rep hit, but you'll probably live.
So the obvious alternative is to extract him from his current extractors. (I'll NPC your muscle if you decide that way so no worries about you having no firepower - although you'd probably need to make a short trip to get some heavier weaponry)
That leads us back to the original quastion. Do you trust them Kot? Are you willing to put Stryker's head in their hands? How about heads of your team?