We analyzed far-UV (FUSE), UV (HST, IUE) and optical spectra of hot massive stars in the Milky Way with non-LTE, line-blanketed models with sphericity and expanding winds. We were able to reconcile previously discrepant diagnostics from Hα to highly ionized transitions (e.g. OVI and NV) with a revised treatement of soft X-rays from shocks and clumping in the stellar wind. These effects could be constrained uniquely by combining lines in the FUSE range and at longer wavelenghs. We derived Teff and luminosity values lower than canonical values, and refined measurements of mass-loss rate. The Teff recalibration of O-type stars has relevant implications for our understanding of massive star evolution and energy balance of HII regions. Mass loss is a major source of uncertainty in our current knowledge of massive stars evolution, and a consistent derivation of mass-loss rate from optical and far-UV lines is an important step forward.