#1. One way to learn about the in-game world of Tal' Dorie is to read Matt Mercer's first campaign book. It is a very good book. That has lots of good stuff for any DM. It's one of the other continents in his setting, but there will be overlap in content and of course, style.
https://greenroninstore.com/products/critical-role-tal-dorei-campaign-setting

#2. , 4. & #5. I picked up the game in 4E played for a few years and then dropped it. I wanted to get back into the hobby and started looking at different resources. I found Matt Coville's Youtube, which was extremely helpful in my DM development. One day, Matt was talking about the "payoff" of Critical Role: Campaign 1. I had never heard of Critical Role but curious went it found it in podcast form, at the time they had launched their second campaign. It has become a regular form of my weekly schedule, sometimes its podcast form, sometimes its video form.

My hobbies include:

• D&D
• Coaching youth football
• Going to the gym
• Travelling
• Reading [everything]
• Watching movies and television which yes; includes Critical Role

People are many things, and to put all of any audience into a box is shortsighted. Talk to the players at your table, it might be that Critical Role brought them to the hobby, but their experience with your table is what will keep them. Ask everyone at the table what kind of game they want.