Here's my advice:
Stop trying to break through. Use sublingual harmalas before you vape. Do smallish doses. Explore that space. The more you spend time in the shallow end, the more you learn it isn't shallow at all. Sub breakthrough with harmalas is where I get all of my important work done. These days, if I break through, it's by accident. With as little as 15mgs in the GVG.
I take sublingual harmalas and set up several 10-15mg doses. The harmalas slow things down and make the space more accessible. It can also be more visionary than hallucinatory, or a mix of the two. The depth is just as profound as a breakthrough, but more interesting. you just have to learn to accept and see the vastness. You need to learn to lay down, close your eyes, keep still and pay attention. Allow the trance to take hold. That was the case for me at least. I get SO much more out of dmt now that I no longer worry about breaking through. Or maybe I have redefined my understanding of "breakthrough."
If you learn to surrender to the substance, you can slip into "breakthrough" or total immersion, from a space you would have previously found dissatisfying. My common dose is between 12-15mgs. Last year I had repeated contact with distinct, named entities. In one case It was a woman named Lupita. Just a woman. Maybe 5' -5", a little bit round. Hispanic or Middle Eastern. The visuals were a bit dim, but not really classic visuals. Whenever I encountered her, it was usually in a sort of physical therapy/massage clinic. Looked like a room. A calendar on the wall, like you might see in a hispanic owned bodega. She would chat with me and work on my body.
She sometimes called in a very intense, stern entity who only approached me from behind. I was instructed not to look at him. Not to address him, but to only answer questions, if asked. She called him "the big guy". Then, later during a protracted period of daily work, she revealed her true self. I had a "breakthrough" on my second 10mg dose (seperated by ~30min from the first) in which I was in a huge cathedral, and she was floating down from above. Pouring blue beams of almost unbearable love into me. She was wearing the classic Virgin Mary gear. I'm not a Christian, and don't know much about the Catholic church. Later I looked up the name "Lupita" and found this: Apparently, in Mexico, Lupita is a nickname for the Virgin Mary. Pretty weird.
Lately, I've been repeatedly visiting some sort of space station in which incredibly lithe alien women instruct me on the nature of grace and other things, while doing incredible acrobatic dances. Some sort of hyperspace martial art.
So... there's plenty of stuff to experience without trying to break through. The experiences I describe usually lack the frightening intensity and state bounded nature of the break through. In other words, you can bring a lot more back. That's something to strive for IMO.
Welcome Home Mister_Niles. We've Been Waiting For You.
"Don't worry. When it happens, you won't be able to not let it do its thing. You won't have the ability to distinguish a pen from a hippopotamus"
- Art Van D'lay