Did it. I used the gun to shoot the virus and dropped it after. After deleting the edvidence, I ran up to the mansion, grabbed the VHS tapes and played the tapes. I hid in Francesca's room, and after SC dismissed his guards, I lured the blue guard into the room, knocked him out and hid the body. After subduing the Chef, I called Silvio to lunch, poisoning his other guard's drink with the sedative. I threw a kitchen knife into his skull and that was the end of the Genuis.
After dragging him and his bodyguard into the nearby crate, I snuck up to Silvio's office, where Fran eventually showed up. I stabbed her with a letter opener and hid the body. I ran out of the mansion to the car, bursting the staff door open with the Bonaparte. The whole thing took about 30 minutes.