CPU overheating, Possible liquid cooler malfunction

I built my computer about a year ago, and purchased its parts to allow for overclocking. I have a MSI Z170 M5 motherboard with a intel i5-6600k cpu being cooled with a corsair H100i GTX liquid cooler. After i first built my computer, I not only had the game boost on, i also gave it a pretty significant overclock on it. Now about a year and a half later, i was running a pretty cpu intensive game and i look over and the temperature is flying from 80 to 90 degrees C. Im not much of a computer guy so i didn't know that that was high for core temp, i just have a little two digit readout on the motherboard i can see while gaming. I tell one of my friends and they freak out and tell me im going to kill my processor. So I turn off game boost and the overclock resetting everything i could in my computer to default. When the game boost is off, it idles around 50 and plays games at around 70. I read alot online about the possible causes of this overheating but nothing was definitive, so i decided to see if i could run a cpu test while overclocked and after i booted it in game boost, right as it started up the temperatures climbed to slightly over 100. I turned off game boost and restarted it as fast as i could. Trying to find out if my pump is broken, i felt the temperature of the heat sink, which was cool to the touch. I felt the temperature of each tube from the pump to the sink, and one was hot and one was cold, leading me to believe that something is wrong with the pump. Another thing i noticed is my cpu and is and memory are reaching 100 percent a whole lot more easily than they used to. Thank you for reading all of that, i just wanted to make sure i gave all the pertinent information. I have three questions. 1) How can i be sure my pump is broken and i need to buy a new one? 2) Could my week or so of playing with extremely high core temp have damaged my CPU, and how can i tell? 3) Is there anything that can be done to repair the damage to the pump or the CPU? Thank you for your time. I want to get back to overclocking my cpu and playing games the way they where meant to be played.