To the OP, have you thought long and hard about this decision? What aspects of PT do you perceive will make you "happier" or lead to a more fulfilling career than being a physician?
As it relates to the DC vs. DPT thing, there are a number of fundamental differences between being a chiropractor and a physical therapist. Honestly so many that I really don't even want to delve into them. DCs ultimate claim to fame is that most, if not all, pathology stems from the spine or the nervous system. At least that is how it has been explained to me by DCs, DC students, and anecdotal accounts. So maybe your common cold or flu is caused by some spinal misalignment. Maybe your cancer or other cellular pathology is caused by some trauma to the nervous system or spine.
The foundation of physical therapy, as it practiced today, is movement functionality. Physical therapists are fundamentally concerned with the anatomical(namely MSK, NMSC, Integ anatomy), physiological, and neurological pathologies associated with how people move on a daily basis. That movement/movement pathology can range on a continuum from ADLs to the very complex biomechanics of throwing a football or baseball at the professional level. There are obviously a multitude of movements set up along that continuum. There is some overlap, though, between chiro and PT. There is still a battle about who can and cannot do manipulations. Around and round we go, when will it stop nobody knows!
Many argue that PT has a much stronger scientific base for some of its interventions than chiropractors. This is one of the reasons why the medical community appears to much more accepting of PT than chiros. There are other historical factors that are political in nature that also play a role as well. Bottom line, human being were designed to move. If we do not move, there is insurmountable evidence to suggest that any number of pathologies will ensue. PTs and PT researchers spend their careers facilitating and assessing movement in patients.
BTW, that is a very simplified version of both professions!