the way i read your question, the only class you will not have mostly completed by the april MCAT is orgo 2? orgo 1 and cell bio will almost be over by then and a good bit of the material learned. if you are legitamtely spending 20 hrs a week right now, i think your plan to take the mcat in april is realistic. you sound very dedicated and if you take the april MCAT you will have more time to get clinical/volunteer experience over the summer to bolster you app. as far as UNC goes, it is an extremely competitive public school. for the class of 2008, UNC received 750 in-state applicants, interviewed 430 and 136 matriculated according to the MSAR. the median gpa for UNC 2008 was 3.65cum/3.64sci. the median MCATs were 10v, 10ps, 11 bs, P. keep in mind a place like UCLA received 2413 out-of-state applications for 23 spots in its class of 2008 and its median gpas were 3.8cum/3.8 sci with med MCAT 10v, 12ps, 12bs, Q. these medians include in-staters so you can assume oos applicants had much higher median scores.
Edit: Info on schools from 2006-2007 MSAR