Firstly, only basic mathematics is required. You can use the 4-2 Rule (accurate to within 1% for 9 outs or less). Do some work on how incorporating FE and bluffing reduces the amount of equity you need. in depth maths would be required for advanced post-session analysis

Regarding nonverbal communication, NVC. From my experience:

1) There are definite physical tells that will allow you to make the 'perfect' decision in a given hand. You require knowledge of NVC, skill of awareness and observation and the ability to put all the info together accurately and make the best decision given all those factors. this takes time, can be tough but can be learnt. Any action that is physical i deem a tell if it reveals something about my opponents play/hand strength etc BETTING ACTIONS are incredibly important to watch. There is so much info just watching a player's hands and how they handle the chips - this might be enough. 

2) The CHANGE in behaviour is important. The onset of the emotion, the demeanour of the player etc. Instead of thinking he did this and it means this, INSTEAD think 'he has been doing this (baseline behaviour) and now he is doing this (some deviation from the norm)' - part of NVC theory, but thats the gist of it

3) use NVC in context with your poker theory. bring everything together

4) understand that NVC is a skill like any other and it takes time to get better. you will make mistakes weighting the factors differently HOWEVER just like we group players online so i noticed similar tells exhibited by similar-type players. 

5) Where it goes wrong:

a) Beginners/inexperienced recreational players are overwhelmed by emotions and as such are a nervous wreck. They give off heaps of tells and it can be overwhelming watching them.

b) Beware of generally accepted 'tells' of weak or strong. There is plenty of info that is just plain wrong. Eg the 'nervous/shaking hand' is usually very strong (and not weakness) as adrenaline has been released into the body after making a big hand. 

c)... i'm tired PM for more info, there is so much i could write on this topic

Live tells are usually most useful when you have a very close decision.