What does "I bet ~" mean?

Why does "now" appear at the beginning of the sentence? Is it common to put "now" like this?

"Now" here is used at the beginning of the sentence to draw attention to what the speaker is going to say. "Now" was used like this often in the early to mid 20th century, but using "now" like this is not common anymore.

What does "norms" mean here?

The word "norms" means a pattern, behaviour or expectation that is regarded as typical or that is seen as "acceptable" or "right" according to some group. In this case the group "global" means the world or society. Ex: These days families where both parents work is the norm. Ex: We all have to live our lives according to social norms.

What's "allusion" mean?

An "allusion" brings something to mind without mentioning it explicitly; an indirect reference. Ex: Irene made an allusion to having a boyfriend, but she didn't confirm it. Ex: The artist makes allusions to freedom in their carefree painting.

What's the difference between "holocausto" and "massacre"?

These two words are similar in meaning. A "holocaust" is a mass murder or slaughter of many people. It also can mean a very large destruction using heat or fire. A "massacre" is the act of killing many people. Ex: The Holocaust was one of the greatest tragedies in history. Ex: The Boston massacre was the tipping point for the colonies' rebellion.

What does "be likely to stick" mean?

"Be likely to stick" in this scenario means to be likely to continue to do something; to get into a habit of doing something. Matt is telling his audience that if they were to make small, sustainable changes, they will get into the habit of continuing these changes and learning something new. Ex: The information is more likely to stick if you were to apply it to real life. Ex: Flossing your teeth is more likely to stick if you flossed every night.