I am looking to install the Dacor distinctive gas range and I am concerned about the hood. Ideally I don't want to install a hood in the short term and I am trying to determine if it is safe to simply keep my existing vented microwave above the range. It is currently vented to the outside and I think it is 300 cfm. In addition there are two windows in the kitchen. I guess what I don't fully understand about the hood is if it's purpose is to reduce heat and smoke and/or is it to prevent fires. i.e. is the hood more of a recommendation for smoke reasons or is it a requirement for fire safety.

The hood is there to provide a fire resistans surface in the case of flare-ups and to vent out odors and smoke. Your microhood serves the same purpose as a regular hood and can be used above your new range.

It's also there to remove moisure while cooking.
Excess moisture can cause moisture to form on the glass on your windows and to the extreme, mold to be more likly to form.

I have a dacor too. You need to check the manual for the minimum height between the top of the stove and the bottom of the vent assembly. Depending on the range, this can be an issue. The beefier the range, the bigger the height.