How should I adjust the cooking time - it was still very wet?

I have a gas oven and followed the recipe exactly (even used a 6" cake pan). At the end of the 40 minutes at 300, the cake was still very wet. I added 4-5 minutes at a time, for at least 20 minutes in order to get it "mostly dry with a few crumbs hanging on." By this time the top had gotten quite brown (not burned) but cracked open enough that it was too dry and large chunks falling off upon inversion. Also, the entire equator of the cake was puckered in like a band had been tied around its waist. What went wrong? Should I increase the bake time during the 25 minutes at 325 or only during the 400 minutes at 300 or split evenly between both? Otherwise the texture was very nice, but not "jiggly" like it should have been.
Also - my batter rose up over the top of the pan and stuck to the top rim of the pan which I had not buttered (had only done the inside/sides). Next time I will definitely butter the entire curled rim so it doesn't stick - this was critical during the removal process - should be noted in the instructions.
Otherwise this cake was incredible - beautiful flavor, not too sweet, unique texture. Will definitely make again and again.