Can’t be done that far back, due to perturbations in the orbit.
See for example
https://en.m.wikipedia.org/wiki/Halley%27s_Comet
“...Researchers in 1981 attempting to calculate the past orbits of Halley by numerical integration starting from accurate observations in the seventeenth and eighteenth centuries could not produce accurate results further back than 837 due to a close approach to Earth in that year...” and
“...In 1989, Boris Chirikov and Vitaly Vecheslavov performed an analysis of 46 apparitions of Halley's Comet taken from historical records and computer simulations. These studies showed that its dynamics were chaotic and unpredictable on long timescales...”
I can recall reading both of these analyses. In effect, ultimately the orbit of Halley’s Comet (and most other comets) are perturbed by the masses of the larger planets in ways that make the orbit unstable and unpredictable - in much the same way as the classic mathematics problem of the orbits of 3-bodies are known to be unstable (usually the lightest one ends up being ejected from the system).