are you checking your temps whilst running prime95?
if its blue screening when you put your cpu to %100 load then its not a good overclock, you might need to bump your voltage a little
seems like you have hit a wall, try dropping the overclock down a bit then run prime95 and keep doing so until it becomes stable
once you have it stable try increase your voltage by .10 then try a little more overclock until it becomes unstable again then drop it back until its stable
increase your voltage by a further .10 then repeate the process until you have a nice stable overclock!
check out the max voltage your cpu is capable of handling and keep an eye on your temps at full load
its basicly up to you, i wouldnt take it much higher with your temps being 63 there is room for a little more but not a great load!
When we used to OC a couple years ago, who never let the CPU get above 50C. Newer CPUs do have higher tolerances, but I personally wouldn't run anything above 55c.
Why is your motherboard getting so hot? Is your room 90 degrees in there? You need better case cooling and your CPU temps will also drop like a stone.
My case runs 35c, because it's in my basement which is about 75f so a little on the warm side as an ambient room temp.
Open the case up and stick a 110v AC huge fan beside it blowing in there if you have to.
What is your CPU North bridge speed?
FWIW, there's nothing wrong at all with 60c as a max load temp. Get used to it with a 1st gen Phenom, they run hot. An aftermarket cooler right now won't help a whole lot with the case temp being 50c. Whatever cooler you have seems to actually be doing a decent job to keep it within 13c of the case temp at full load.
I had a 7750 Kuma and could clock it to 3.4ghz no problem, so IMO something is wrong with your setup unless for some reason the 7850 doesn't have as much overclocking headroom which would be weird.