I haven't messed with cart/atomizer setups too much to be able to give u advice on filling and whatnot. I started straight off dripping, but whenever I did try using carts I never had good consistent wicking. Then again, I went right to low resistance atties fairly early on. Sounds like you may be flooding it out.
Even though you may have to fill up more often, you have more control of your vape with direct dripping. I love the flavor of the ego mega type b atties, on first use id reccommend dripping around 7-10 drops first use and anywhere from 3-4 drops when flavor starts to weaken. Seeing as these atties hold so much liquid its good to blow them out every once in a while from the part you vape out of thru the battery dide. Juice tends to build up in there, get really gurgly and just end up leaking out. It might not seem like it now but I think dripping is way easier to get the hang of than using carts.
And +1 for the ego mega dual coil cartomizers, I bought 8 for around 20 bux over a month ago and I am still using and reusing these puppies. No cleaning, nothing - just refill after refill. thats if u have a genuine joye ego tho, I hear some ppl have problems with rivas and other ego clones making contact to the battery (requires modification or an adapter) good luck to ya!