Yep, I did as well, as I have no plans to expand or continue work on 3D either, and just getting Zbrush was a bit of a hassle. Pretty expensive too. You could use blender, most people seem to switch to that.
Granted, I had previously learned 3D studio and Maya, so I was familiar with working with 3D space, and even if you don't dedicate your career to it, I have to say becoming familiar with a 3D tool does help improve spatial awareness.
Still, to each their own, we all kinda follow the course in different ways. In that respect, I don't remember if you mentioned it, but are you following the Study companion? if not, I would recommend to try it out, as it expands on the course significantly, and though there is some repetition, I've noticed it has helped me improve considerably than if I had only followed the course videos and basic exercices.
I would also recommend taking a peak at how some others have tackled some of these exercices and references, some have done some truly impressive work, and seeing how others do it also helps take tips from them for your own work.
Exercices look good so far, anatomy is quite a challenge, but also a lot of fun.
