1) yes. Hovering over the tooltip will display the amount you would gain. This is halved for each pleasure dome currently on the map.

2) Once a company has a patent it is unavailable to any other company. Future patches will likely change this, but for now yes.

3) No. The colonys demands increase the more colony buildings there are. The colony slowly builds buildings overtime on their own in multiplayer, and in the campaign you can build those manually. This increases the demands of the colony

1) the income from pleasure domes is n*population, where population is colony pop plus 5 from a scientific lv 5 HQ, 10 from an expansive lv 5 HQ and 15 from a scav lv 5 HQ. There is an additional 1 phantom population (I suspect it is an extraterrestrial that visits the pleasure dome some times.) n is the number of pleasure domes + 3 divided by the number of pleasure domes. So at 1 dome, income is 4*pop, at 2 domes it is 2.5*pop and the lower limit is 1*pop.

This means they are justifiably not-bad for you in scav vs scav 1v1s (when you have some source of abundant power) and also in FFAs with a lot of expansives/scavs.

3) The colony is fairly insignificant in MP. In the campaign it grows a little slower if life support is expensive, it is not directly influenced by anything players do but only by the price of construction materials (alu, glass & steel) and life support (water, food & oxygen).