yes, he has sage mode. he experimented on juugo and other ninjas to obtain it. it was probably part of his goal to control senju dna (ref: yamato experiments) the curse mark is the application of juugo's ability, i.e. sage mode, to a person other than himself.
another reason is oro probably tried to learn sage mode after seeing jiraiya use it.
orochimaru's sage mode is inferior to kabuto's because kabuto trained with the snake sage, which oro hasnt done. kabuto's sage mode is as real as oro's, namely, obtained through unholy science rather than learned through meditation.