Don't always trust what speedfan tells you
On my PC it tells me temp2 is 127C, which is complete and utter bullshit
I doubt your PC would survice at 114C
Anyway, about the case, trust me it's safe to turn on a PC without the case on. as long as you don't start poking in it with your fingers, that is
The case is just to protect against things touching important parts and stuff, and it's better for the airflow. but a PC can run fine without a case