Maximum power dissipation

I simply put in a reasonable temperature range. Generally, a Dev.Kit isn't a professionel instrument. It must not be expected to be operated at extreme temperatures, most likely it isn't even operated continuously. On the other hand, the FPGA chip won't be immediately damaged when the specified max. junction temperature is exceeded.

Yes, I think you are able to overheat the Dev. Kit by running a design with high power consumption. I don't think, that an explicite warning is required. I didn't yet hear of a Dev. Kit that has been damaged this way, but it's possible at least.