Sorry, I haven't read the entire thread yet, but here's my take.
I'm not sure about the idea of psychedelics allowing us entry into different dimensions, but have less problems with the idea that they could allow us to see things in different spectrums that are always there but we are unaware. Similar to how humans can only hear certain frequencies and see certain wavelengths as these are all merely electrical signals interpreted by our brain and our brains are likely filtering out millions of pieces of info a day/hour/sec that we wouldn't be able to process it all.