I understand the frustration. So close yet still not there. I use a tool kit by Platinum Tools part number 19101. It has a neck that extends around 5 inches and has a thin neck like the one you use. You can get a little bit of help getting to it if your have the twin G5 Logos on the to of the heatsinks instead of the large single cover. You can unclip the G5 logo caps by just unclipping the two plastic clips at each end of each one. Just a small screw driver will do it and they will both just lift off. That will open the area up for you to get at it easier. That will give you a whole lot more room and you can most likely use the Extension that comes with your iFix it tool kit.
Good luck