I have lots of different Inov-8s. The Standard Fit pairs are all standard sizing with wide and very comfortable toe-boxes. The one Precision Fit pair I bought (a mistake) are definitely too tight on the toes.
For me it generally works to go half a size down compared to all other brands I have bought.
That's perfectly accurate - but it does depend on your tent. I had a cheapo tent with little ventilation but still managed OK. Best to go for one with a mesh inner that you can leave the outer off, as long as it doesn't rain. The race is run in the dry season but it is still the rain forest. We had 2 nights of rain out of the six.
I did the TCC this year but only the shorter category, so my training regime may not be so relevant. Days 1 and 6 were the same for us but the other days we joined further along the course, at checkpoint 1, or 2.
Many people found the heat a real challenge (high 30s, total humidity) but I strangely liked this. What was a real challenge were the hills though - very steep, very long. If I knew then what I know now I would have done a lot more hill training including speed hiking for those sections just too steep to run. Some kind of practice tackling technical single-track downhills - rocks and jungle - would help to, though can't really replicate that here.
The only other thing I would change would be to take a bigger and airier tent - unless you like trying to sleep in a sweatbox!