Never done DMT, seen a bunch of documentaries and have read many articles. My Question is: do you personally believe that DMT is a chemical gateway to the spirit world, or do you believe that you're just simply tripping on DMT? This is a question only for people who've used DMT.
The questions you ask present a dichotomy which I'm not sure accurately reflects the experience. I will say that DMT is a pharmacological substance, so the the condition of "tripping on DMT is satisfied." Now in regards to the rest of it... I sit on the fence in regards to where the DMT trip takes me. I am not as convinced with the camp which suggests the visual phenomena of psychedelics is sub-conscious manifestations built up from your current emotional/psychological mental status with DMT as I am with Mushrooms and LSD. I consistently experience incredibly intricate, complex, geometrical shapes and patterns on DMT in a degree of perfection which is just not really of my character nor particularly like most other psychedelics at the respective doses I have explored. These shapes and patterns quickly develop into apparent structures which seemingly appear to be made out of 'rules' of architecture, which is often much more polished, detailed, elaborate, etc. then I can really attribute to anything in the scope of the structure and designs I experience in normal reality. Then less frequently but on occassion there is the experience of interacting and seeing sentient things emerge from all this. So this level of perspective can certainly be 'spiritual' and the appearance can be that of a fully immersive 'realm'. With that said, I do not think my mind, completely detaches from the body to freely roam in the DMT experience. Furthermore, my heavy doses of Salvia Divinorum have provided me a similarly convincing 'realm' so I don't think there is an inherent 'higher realm' DMT takes me to. At my most speculative, I think DMT possibly opens one up to new dimension (s). The 'flood' of exongenous DMT which is a chemical that is normally broken down in the gut before reaching upon the blood-brain barrier, overwhelms our brains which is not evolutionarily equipped to handle the bypassed method of smoked/freebased DMT and this limitation of processing also perhaps exposes the limitations of cells and particles reisiding in our brain and bodies, which are disrupted from the homeostatic functioning of working in concert during our normal processing of inside and outside awareness. I think this suggests how delicate our neural framework is and that the constiuent parts of cells are not necessarily made to understand the cognitive processing of the human which they reside in, that most of the expression of our functioning revolves around response to enviornmental pressures. I also do not think the DMT realm is one that can be brought about by other methods so there is an intangibility about it that is not particularly comforting and while I think it can be an incredibly profound experience, I would not see it as feasible to center your spiritual life around. (Although some do for Ayahuasca, the slower, longer lasting oral DMT +MAOI brew) Perhaps if/when technology progresses there could be a way to gauge if DMT shows a free standing reality, or how the mind orders information in such a way but given the nature of the drug war and limits of current technology, probably won't happen within our lifetime.
short answer: your just tripping on DMT. long answer: I believe DMT and other psychedelics can allow one access to aspects of their own consciousness and mechanisms of psychological nature. the experience can shift ones perspective to "alternate" levels of abstraction, or at least ones perspective in the hierarchy of levels in a "strange loop" sort of fashion in that it's not always apparent where exactly your perspective resides in this hierarchy due to the complexity of the systems involved. for a minute, attempt to ponder a sequence of fast arpeggios in different musical scales. played at a fast enough rate, these arpeggios will be percieved as roughly a single note, the sequence of arpeggios making up a chord will be perceived as a single note which may be perceived as part of a certain musical scale themselves. if you slow it down though, you will have a different perspective of awareness, and each note will then be expanded to be it's own sequence. moving the opposite direction and adding even more complexity and higher rate of speed, one can reach even higher levels of abstraction.
biochemistry is physical. sprit is spirit. kind of simple that. if we blind ourselves by expectations, and chemistry inhibits our doing so, well that's fine. but it isn't spirit that is changing, only what we think we see.