I think that list is correct and you should prioritize this list depending on your business. In addition to the above, I would advise getting a tool like Chorus.ai or Gong.io. Chorus or Gong will help you scale as your team scales in getting customer feedback both on the new business side as well as current business. In reality, you can't be on all the great calls as that is physically impossible.
A few other things to consider:
Love what you have already! Do you have budget for qual research incentives? This is a huge gift if you can offer $100 to target personas to provide feedback on messaging, or to prospects for win/loss interviews, etc. Also consider a recruiting tool like Respondent.io if you are running out of low-hanging fruit from networking / site pop-ups / LinkedIn recruiting.
Oh I love this question! For me, my background is in both PMM and PM... and I believe that my future will be too. As you continue in your product career, you'll find that every organization has their own "classification" of these two roles and that a lot of the responsibilities really blend across the two teams. Sometimes PMM is responsible for pricing, sometimes PM is. Sometimes PMM is responsible for competitive intel, sometimes PM is. So, it's really about what you like about your PMM role and finding an organization that aligns to that.
I suppose that answer varies for everyone. For me, it was simply about being more comfortable with marketing than with product management. I didn’t really know what product marketing was until a few years into my marketing career but once I got into it, I loved it. In hindsight, I don't regret it for a second. Having said that, there is obviously an overlap and each position must intimately understand the other.