Important: if your ice cream remains dry and crumbly after you run the mix-ins function (or choose to not add any mix-ins), add a splash of whichever milk you prefer, and process it again using the “re-spin” setting.
If you don't have a whey/casein blend protein powder, firstly, I highly suggest you get some! PEScience is a great brand. Next best thing is to get whey (which you probably already have) and casein protein (which you probably don't) and just mix them 50/50. All else fails, you can try just whey, but no promises it'll turn out great!
The point of step 5—thawing out the edges—is to loosen up the parts of the mixture that have frozen to the walls of the container. If you don’t, they’ll stick and won’t be processed correctly, leading to chunks of ice along the walls, which suck!
Whatever mix-ins or toppings you add are not included in the calories/macros above. However, it’s honestly pretty difficult to add so many mix-ins that the macros become “bad”. For instance, you really only need 2 Oreo Thins mixed-in and 1 crushed up on top to make cookies and cream, and that only adds about 100 calories for a total of 305 calories and 35g of protein. That’s still way better than the vast majority of protein bars!