  Context. Obtaining precise stellar and wind properties and abundance patterns
of massive stars is crucial to understanding their nature and interactions with
their environments, as well as to constrain their evolutionary paths and
end-products.
  Aims. To enable higher versatility and precision of the complete UV to
optical range, we improve our NLTE atmosphere and spectrum synthesis code
FASTWIND. We also aim to obtain an advanced description of X-ray emission from
wind-embedded shocks.
  Methods. We include a detailed comoving frame radiative transfer for the
essential frequency range, but still apply methods that enable low turnaround
times.
  Results. In most cases, our new results agree excellently with those from the
alternative code CMFGEN, both regarding the total radiative acceleration,
strategic optical lines, and the UV-range. The agreement regarding
NIII4634-4640-4642 has improved, though there are still certain discrepancies,
mostly related to line overlap effects in the extreme ultraviolet. In the UV
range of our coolest models, we find differences in the predicted depression of
the pseudo-continuum, most pronounced around Ly_alpha. The comparison between
our new and previous FASTWIND version reveals an almost perfect agreement,
except for NV 4603-4619. Using an improved, depth-dependent description for the
filling factors of hot, X-ray emitting material, we confirm previous analytic
scaling relations with our numerical models.
  Conclusions. We warn against uncritically relying on transitions, which are
strongly affected by direct or indirect line-overlap effects. The predicted
UV-continuum depression for the coolest grid-models needs to be checked, both
observationally, and regarding the underlying atomic data. Wind lines from
"super-ionized" ions such as OVI can, in principle, be used to constrain the
distribution of wind-embedded shocks.
