It is fairly normal, even 7C diff is acceptable. Less is better. I wouldn't wory about it, your temps are below the acceptable limits?
Spreading the paste isn't the best way.
A blob bigger than a grain of rice, smaller than a small pea in the middle is what you need. Put the cooler on nice and smooth and it will spread out fine. Making a thin layer could make bubbles.
how much is smaller than a small pea ?
a Russian pea could be very different from an Australian pea from an Brazilian pea ?
so how do i get the size of thermal paste compared to that pea you are talking about ?