In my case, it was pretty easy to get off venlafaxine. Not to diminish your experience, which I am truly sorry to hear about. I was on venlafaxine for about a year and a half, with a peak daily dose of 375 mg. I do think it made my suicidality worse at the start, but at least getting off it was easy for me.
...what in the tar of nation! Such concentrations are not even available here, with 150 being the max dosage for Effexor. I would probably just collapse and die if I tried to wean off of 375 mg of venlafaxine.