I know how to remove it, and you have tried some harder stuff then what you had to.

Find the tinyest and more "solid" knife you can(it as to be very tiny and very solid...). and then, you that the corner that is opposing the "cutted corner", and you just take the knife blade between the IHS and actual CPU, and you do like a saw(Sorry, I dont know how to spell the manual wood cutter(?)), and after you got as deep as 0.5CM, you do the lever trick(it mulplies your actual force by about 10x), and it should come off.

BTW: The epoxy will resist to about -60C.