For fireworks, it's been where the map is showing as well as on the right side (though not shown on this map) for a while now. It's not directly in front of the ice cream shop nor Casey's, but a couple of sections forward. I've never found it to get too crowded because they limit the amount of guests. People often arrive at least an hour before fireworks. Depending on the crowd level for the day, we've gotten in 45 min early and gotten turned away 30 in advance. It really depends on the day. I've made it a point to aim for arriving 45 min- an hour early. All that being said, we haven't watched fireworks since the parade started. I'm not sure how folks are managing that since the disability viewing areas for the parade and fireworks are in different places. I suppose one could watch the parade from the fireworks viewing area if you went to the ends of the roped off area in the disability section where Main St is, but the risk is people will be standing in front of you on the sidewalk.
The map may change again. It's best to either see if it's posted on the website or grab one when you enter the park to see if there have been changes. I'm fairly certain the disability fireworks viewing area is unlikely to change and the disability parade viewing area in Frontierland (across from Hall of Presidents) is unlikely to change because those have both been established where they are for a while now. It's just always a good idea to verify it well in advance of the shows though.