It's doable, but I think you should definitely drop a section. Rather than going through Salzburg, Vienna, and Hallstatt, you should consider basing yourself in one place for a longer time and doing a few long day-trips. It's far more relaxing to return to the same hotel in the evening instead of packing up all your stuff and moving on to a new town.
I have never been to Hallstatt but Vienna would be my choice to skip. I lived in Prague when I visited it so I had pretty high standards, but it seemed to be just like many central European cities but more expensive. Ljubljana is a good place to be a base for day trips. You can take trips to the sea and to the mountains in a day, comfortably.














