Thats quite a lot of info, nice job! Id just like to add one tiny thing. The reason those resin glands are there is a trait by the plant that during the end of flowering season, those glands are created to protect the plant from the sun's rays. Like you mentioned early on, the most potent plants are usually found in equatorial places, or regions of high altitude, where there is a large amount of direct sunlight. Exlcuding all the chemistry stuff you mentioned, the mroe intense the light during the flowering period, the larger the trichomes will get because the resin glands will be working overtime. This results in a LOT of THC production.
"So it could be GENE protection...thc.. i mean from all of this it seems as though above 270nm uvb/ uva will cause DNA damage.... So by producing thc the plant can effectivly reflect harmful UVB`s UVA`s.... "
Right on there. Harmful rays from the sun give you skin cancer, and are the reason you smoke cannabis! Like most weeds, this is one of those genetic traits designed to keep their species thriving.
And like you also mentioned early on, moisture levels do matter. Not watering your plant the last week or so of flowering will make the plant a lot drier inside, which means the light will have more effect and will heat up the epidermis of the plant. This stimulates the resin glands to produce more juicy trichomeness to reflect the light and lower the temperature of the plant. These are just some of my theories i have picked up on by reading threads like this.

Nice post dude. +rep