Spitting and popping is the result of a flooded coil. Too much juice is reaching the coil at once and it isn't converting to vapor fast enough. Instead you get bubbling juice at the coil, kind of like boiling water in a pan. Vapor will build up under the liquid juice and pop through the surface tension, and that's where the spitting comes from.
The two best ways to prevent spitting is to either change the mix or increase the wattage so the juice vaporizes faster. The problem with increasing the wattage is it can lead to dry or burnt hits really quickly. Changing the juice mixture is better because the results are more consistent.
I would definitely recommend a higher VG juice. I vape an 80VG/20PG mix in mine and never get any spitting or popping. I would think the very least you would want would be a 50/50 mix or perhaps a 60/40 VG to PG mix. Subohm tanks really aren't made for runny high PG mixes.
I really can't compare your wattage with mine since I use SSOCC Ni200 coils. With temperature control my wattage fluctuates like crazy, but I have it set at 35W to get instant vapor. As soon as the coil reaches the set temperature it adjusts the wattage to maintain that temperature.