I've only recently started doing this, but I like it so much that I might not ever go back to vaping freebase without harmalas . My recipe has been 100-150mg harmaline followed by 18-24mg DMT vaporized about 1-1.5hrs afterwards. I wait a little bit longer with the DMT than is generally advised, because fasting for 4+ hours isn't an option for me for several reasons, and I want to make sure the harmalas are in full effect when I vape. It is my understanding that harmalas work 4+ hours anyway.

I prefer harmalas+DMT to just DMT for a couple of reasons. The coming-up is markedly slower for me (instead of 15 seconds probably around 40 seconds, which makes a large difference) so I can ease into it, i.e. it allows me to do away with the "what have I done to myself" feelings before I really plateau. Secondly, because the whole experience lasts a lot longer, I'm able to get much more out of it. With just DMT I often feel as if I've seen/understood/experienced only a glimpse of what was there, simply because it was gone so fast. Much less so with the extending action of harmalas.

About your dark journey, I think that's just a part of the DMT experience.. I've had it happen on just DMT, and I have no doubt at all that at some point it WILL happen to me when combined with harmalas as well. The general advice is to take a longer break than usual before your next journey, and start slowly next time. Sometimes you can figure out what was the cause of a dark journey (for me it's often inability to let go, the solution is to take control) but I've also had experiences where I still haven't a clue why they turned out as bad as they did. Personally, I wouldn't completely give up on the harmala+DMT combination though, give it a rest and try again at a lower level!