Cooling your body down before going to bed will have the opposite effect if your goal is to go to sleep. By cooling your body it will start to try and warm itself and trigger a stress reaction. Eating and working out before bed will similarly raise your heart rate and sympathetic nervous system activity, the opposite of what you want. Sleeping pills are also bad for sleep, ask any sleep doctor. They are great and knocking you out, but that's not what sleep is.
Saying you did "meditation" for a year doesn't tell us much, just the same as you saying you "exercised" for 4.5 hours a week doesn't tell us much. Both of those terms can mean a great number of things qualitatively speaking.
Counter-intuitively you could warm yourself 1-2 hours before bed with a hot bath or sauna session. This triggers the body to bring blood closer to the surface and extremities to shed heat, in effect "helping" the body cool itself as it approaches bedtime.
Based on these observations I think maybe you haven't tried "absolutely positively everything". And even with all the environmental and body things you've tried, the mental aspect cannot be understated.
EDIT: based on some of the replies about temperature. The hot bath method because it will help your body cool in a physiological way while a cold bath will do the opposite. A cool environment will do the same while a hot one will do the opposite. So hot bath 1-2 hours before bed and lower the room temp for the best of both worlds. Some people go further with chilled blankets such as the Ooler.