One variable not mentioned here is the increasing ∆V of ion thrusters on satellites. On the starling launches 60 satellites all just take off and find their own orbits. The better electric propulsion gets, the less important it will be to lift into exactly the right orbit.
No, but nuclear pulse propulsion could do far more than that.
Back in the 1960s, some rocket scientists working for the US government experimented with theoretical designs for rockets propelled by small nuclear explosives, going so far as to test small-scale models that used conventional chemical explosives, before the program was cancelled due to the ...
Is there any current launch system that could get a 75,000 kg object to geostationary orbit?
No. (Starship/Super Heavy can, of course, do anything, but it's not a current launch system.)
If not, am I correct in assuming the Saturn V could have gotten such
an object there?
According to the Silverbird calculator, a Saturn V could get about ...