1. If humans arose from more primitive animals, why just in one spot near the equator? Why didn't the monkeys we came from migrate first?
2. I'm pretty sure C14 dating is not accurate for samples over 40,000 years old (its actually never been proven accurate for samples over 2000 years old) so this is based on archeological evidence for the 80,000 years ago mark? How do you know that the flood did not skew these results...
3. DNA is DNA wherever it is in the cell, it is extremely susceptible to damage and mitochondrial DNA is especially conserved through species and even more within the human race. If you are using this to track migration, its more likely that you're seeing different results from mutation than place of origin...
I'll take a whack, though I am a scientist not an "anti-creationism person":
1. Monkeys didn't migrate because that would mean leaving the forests, to which they had adapted tens of millions of years ago. Humans are descended from apes who were squeezed out of the African forests when climate change reduced the size of the forests something like 5 or 6 million years ago. Over time they adapted to savanna conditions, developed bipedal locomotion, and thus were able to spread out where monkeys and apes were not.
2. Carbon 14 dating goes back some 50,000 years. It has been shown to be accurate through tree ring dating and calibration in various parts of the world. In the US it has been calibrated against tree rings from standing deal bristlecone pines past 12,000 years ago. In the old world it has been extended even older using tree rings and glacial varves. Thus, it has been shown to be accurate past 2,000 years. As for the "global flood" -- there is no scientific evidence for any such flood. That is a religious belief. (If you have any specific questions on Carbon 14 dating let me know, as I do a lot of it.)
3. There are areas in mitochondrial DNA (which is made up of 16,568 base pairs) in which slight changes are significantly more common. These are called the hypervariable regions. Most mtDNA studies on humans use what are now called HVR-1 and HVR-2. Specific mutations are passed on to all female descendants, and allow populations to be tracked through time. As an example, one individual from southern Alaska, dated to 10,300 years ago, was found to have a particular haplotype of haplogroup D; that haplotype has been found in living individuals from British Columbia to the tip of South America. I have another case of basal haplogroup A dating from 5,300 years ago being found in living individuals in California.
Hope this helps.