Run LinX with Hardware Monitor, Real Temp or Core Temp running in the background and post a screenshot to prove those temps or they never happened.
LinX -
http://www.youwatched.com/datajay/linx(0.64).7z
Hardware Monitor -
CPUID
Real Temp -
Real Temp - CPU temperature monitoring
Core Temp -
Core Temp
You want the heatspreader to be almost fully covered, see my pic above.
After you attach the heatsink twist it a little, if possible. Then run the PC for a few minutes, turn it off and while it's still warm twist the heatsink again, if possible. This will help speed up the "curing process" so to speak.
Everytime the cpu heats up and cools down the paste will thin and thicken resulting in a small redistribution of the paste each time. Pastes like TX-2 will cure almost immediately, within the first 2 or 3 power on & off cycles. Pastes like Arctic Silver 5 won't fully cure until the PC has cycled on & off 10-20 times (or approximately 200 hours of on time).