Has the motor jumped timing?

And my experience with jumping chains is that it takes a lot of throttle to keep it running, not just a lot of timing. Whereas ;
increasing the timing on a properly cam-timed engine will require less throttle to maintain a decent idle-speed. But if the idle speed is too high, and the screw is mostly backed off, then the timing is too much.
If BOTH the timing AND the throttle have to be increased, then the engine is down on idle-power. Could be crossed wires, or compression, but more likely is that there is a load on the engine such as; an overfilled crankcase or a dragging trans.
A locked transmission will try to drive the rear wheels in Neutral. This condition may decrease the idle rpm lower than normal. To get some Idle-power back, the timing will have to be increased and probably the curb-idle as well.
To test for this, get the drive wheels off the ground. Put the trans in Neutral. Now try to bring the timing and idle-speed back to normal.
If you can, and if the wheels, one or both, are spinning, then try the brakes. If the brakes cannot easily stop the wheels or the idle speed drags down, you gotta trans or convertor problem.
Good luck