Hey Lord M - I'm glad you found that critique helpful and were open to it. Just to follow up a bit on the "why" it is best to learn through traditional media and approach. It is really very simple: traditional media are portable, allowing you to study and work from life - anywhere, any time. Traditional media is also faster than digital allowing you to explore more ideas, concepts, compositions, etc. Traditional media teaches you to really see and draw very directly without a cumbersome interface, drawing small, and all the other limitations of working digitally. Learning to really see form, shadow and light is extremely difficult and takes years to begin to understand - it takes tremendous focus and concentration - working directly with a piece of charcoal on a piece of paper - no interface, no distance between the artist and the work. The last main advantage is that traditional media teaches one everything they need to know about the fundamentals of making art - and it does it faster and in a more direct way.
In the end digital media is great - I love it - you can do a lot of really incredible things that you can't do with traditional media - but you have to know what you're doing first. You have to keep in mind it is only a tool - a different medium - and it actually has some serious limitations which make it a poor tool when trying to learn how to really see, draw and paint.
Anyway, I hope that explains some of the "why" behind my earlier advice. Famous Artist Course has some great stuff. My highest recommendation (if you really want to learn the craft) are just two books: "Drawing Essentials" by Deborah Rockman and "Imaginitive Realism" by James Gurney. I know you're pretty serious about improving so just keep at it!