you should never turn your tension dial 2 whole turns at once! you should go about a 1/4 turn at a time & test---you are making HUGE changes at once---and making it very difficult for yourself to find a balance.
the pokies coming through the top on curves is because you are speeding up as you go around the curve---it's normal- to (swoop)- once you get yourself moving at the same speed as the machine that will get much better.
it sounds as if you are trying too much at once-
is there any way you could go to your dealer's for the free (owners classes)? most dealers offer classes to teach you to use your machine- it can make a huge difference in your success.
if you are getting thread nests on the bottom of your quilt your top tension is way too loose---(from turning the dial 2 whole turns!) also----are you using the same thread in the top & bobbin? and the correct size needle for the thread you are using? this can also make a difference-
if you are unsure about thread weights/needle sizes visit Superior Threads web site- they have free charts you can print off telling you the difference in threads and what needle to use with each. it is a great resource.