Use as external monitor for windows

I have an imac from late 2014 and i know and read everywhere that this model does not support Target Display Mode so before knowing this i bought a very expensive hdmi to displayport cable that did not work and i had to return it.

im looking for ideas, hacks, any way possible to use this imac as a monitor for my windows pc that is new and far superior. This imac has a very good screen and i almost never use it, just for some light video editing and if possible i wanted to remove all screens from my table and have just the mac, so if i could use a shortcut go back and forward between the mac and the pc. this would also spare me some cash at the end of the month on the electric bill.

i have an brand new pc the older part is a Geforce 980ti, 32gb ram, 8700k, m.2 drives and all of that.

Any ideas or hacks on how i can manage to put HDMI or dvi into this imac ? surely there must be a way rather than just using remote desktop or something. (that sucks)