Much lower overall GPA is relative. Many of the DO schools have a minimum overall GPA. I do not know them offhand, but they are on the websites. Okay, I did a quick look up. Feel free to confirm them yourself.
UMDNJ - Desired science and cum GPA - 3.0
NSUCOM - Preference will be given to students with a cumulative GPA of 3.0 or higher
NYCOM - Cum and science GPA - 2.75
There are exceptions every year, but try to aim higher than 3.0. It will hurt you if your GPA falls below 3.0. You don't want to be an exception.
Taking courses outside your regular instituion will not hurt as long as its accredited. You must obtain transcripts from all colleges and universities that you attend. Keep that in mind. So, it is 100% reality. Hope this helps.