One God (heis theos). Regular Pauline argument for a universal gospel (Gal 3:20; Rom 3:30; Eph 4:6).
One mediator (heis mesitēs). Late word (Polybius, Philo) from mesos (middle), a middle man. In N.T. only here, Gal 3:20; Heb 8:6; Heb 9:15; Heb 12:24.
Between God and men (theou kai anthrōpōn). Ablative case (though objective genitive may explain it) after mesitēs (notion of separation) as in Rom 10:12; Heb 5:14.
Himself man (anthrōpos). No “himself” (autos) in the Greek.