1. the cas bracket has 1 or 2 aligning pins that have a tendency to seize. Keep working it with PB or wd40 and it will come off. you might have to pry it side to side or wedge a chisel or screwdriver tip between the head and the bracket. Just keep in mind that it is aluminum and breakage is a possibility. Use force but don't go Neanderthal on it.
2. Using an impact should not damage anything. All you are doing is breaking the torque hold on the bolt. After that it will come right out. It is only stuck because the engine is out and that makes counteracting the force very difficult. You can also take the intake valve cover off and use a wrench on the end of the cam to hold it. There is a spot on the front end of the cam with 2 flat sides made for a wrench to fit. Since the engine is on a stand, this would be a good time to do a water line delete, and possibly egr delete and pcv reroute. This would also be a good time to grind the upper plenum to facilitate fuel injector replacement.
