Forget the torque wrench. Just run the nut down and apply just a little more pressure.
Silicone grease, 100% non-handining, should be applied right on the tip of the center conductor. None is needed om the nut threads. The part most vulnerable to galvanic corrosion is the center conductor and socket. To avoid the "air gap," the center white foam dielectric must stick into the center ferule at the botom of the nut. As Londoners say, "MIND THE GAP!"
Place the connection horizontal. Any moisture that gets in runs out.
Personally, for high end installs, everything goes into a weatherproof boxm with bottom entries and exits. The cable and telephone companies learned this a long time ago.