An update on this - me and two friends smoked what was left over and it knocked us into the middle of next week. It seems that i had bad smoking technique, and wasn't letting the DMT fully evaporate when smoking it before, as quite a lot had built up. Anyhow, my friend heated the pipe, the dmt started smoking, he took 3 long hits and was gone. I continued to heat it and let the next guy take two hits and he was gone. While still heating the pipe(its a shake n vape) i took one big hit and immediately felt the effects. So i put the pipe down and blasted off.
We all had a nice experience, and learnt a bit about how to smoke it properly with a vaporizer pipe. I obviously wasn't getting it hot enough when i'd tried before, although i definitely had a breakthrough experience. My friend also showed me his weighed out .1 grams, which was way less than i'd been putting in. So in future i shall be weighing out .05g and no more. As this happened:
About 2 hours after our blast off, my friend decided to be a big man and heated the hell out of the pipe(no more dmt was added, just the residue). He took one massive long hit(there was tons of smoke), then he sat back and made a funny noise. He then proceeded to throw up all over himself and laid shaking for about 20 minutes. The only words he said was 'so this is it, i'm dead'. When he came back round he was paranoid, and accused us of looking at him(we was pretty worried about him). He was totally fine about an hour after, but it just shows how important it is to weigh your dosage correctly. Lesson learned.