Hello Tanya; I have the same board and cpu as you do and had the same ,exact, issue you are describing in your post.
I am almost certain that your overheating problem is not due to a bad TIM application. (although you could take the block back off and verify that you have good TIM spread and surface contact between the chip and block)
The first thing I would do is boot up your pc and go directly into the Bios (Press Delete button upon startup).
Once there take look at your CPU core voltage. If it is reading something like 1.45v at the default Turbo setting, then this more then likely is the main culprit to the overheating problem you are having. Apparently there is a Bios bug with the 4790k and the early bios on the GAMING-GT mobo that applies way more voltage then is needed to the CPU at default settings.
Now check and see if your Bios version is the early F2 version or the latest F5 version. If your board came with the F2 bios? I almost guarantee that this is the main issue and you definitely need to download and flash the F5 version to resolve most issues and allow the 4790k to run like it should.
While your in bios; Disable the Turbo setting and reset the base clock cpu multiplier to x40. You could further set each Core manually to 40 as well, if you want to insure that the cpu doesn`t go above it`s stock 4.0ghz, but may not be necessary providing that you set the base clock multiplier to x40. Auto settings should lower the voltage with these changes to a reasonable level and reduce high heat input to the cpu.
Also; While in Bios don`t forget to disable the Intel graphics to eliminate conflicts with your GTX970 gpu.
Now save the settings and exit Bios and see if you can boot into windows.
Trying not to overwhelm you here to much, but please do try what I described above to see if we can atleast get the heat down and successfully boot into windows.
These are the first steps I took in resolving my issues which were basically identical to what you are posting here.
I am more then happy to assist you further if you like.