You should rinse and spit it out in the morning, don't swallow as you will be swallowing significantly more plaque from the over night build up. After initial morning cleaning swallowing should be fine.
It destroys your heart, possibly. Plaque builds up in arteries, etc. I just don't know if dietary plaque gets into the bloodstream. Don't think there are many studies. But plaque left on the teeth is known to cause heart problems and be lethal so I imagine trying to keep it out of our systems has to be better than not.
