The TWD comic ended. It was a significant moment for fans. The creators decided it was time to bring the story to a close and give it a proper conclusion.
Hard to say for sure, but from what I've seen and heard, it does appear that the TWD comic is nearing its finish. There have been hints and signs that point in that direction.
I have no clear idea about the 'heapsters' in the TWD comic. It could potentially be a nickname for a set of survivors, or perhaps a type of enemy. Without further information, it's hard to say for sure.
Well, the number of TWD comic books keeps changing as new issues come out. But as of the last update I know, there were more than a hundred. The series has been ongoing for some time, so it's hard to give you an exact figure without looking it up specifically.