Bonus Action Spells

You are mostly correct, but there is the small distinction of "turn" and "round". Let me elaborate.

For simplicity's sake, I'm going to commment on your own examples before making some alterations of my own.



Yes, a spell cast as an action does not limit the use of reactions during YOUR TURN.



Indeed, still correct as it is basically the same as number 1. Although the Wizard can no longer cast "Shield" as a reaction on the same round as a character only has one reaction per round.



Correct. Using a Bonus Action spell limits further spell-use, during the character's turn, to a cantrip with the casting time of 1 action. 



Wrong. The wizard can, during his turn, cast "Misty Step" and chose to attack his opponents using a cantrip. On the opponents turn he can still use a reaction, since he hasn't taken a reaction this round, and cast "Shield". This is because the Bonus Action spell imposes a limitation on the wizard during his TURN, not the ROUND. Very tiny distinction. 

I made an excellent scenario describing this, but it seems it was lost to the gods of the internet. 

Anyway, if you look closely at Jeremy Crawford's answer, he probably agrees with me, stating that the use of a Bonus Action spell precludes the use of reactions during the character's turn. 

The relevant example here being:

5. A Wizard casts Misty Step. A Sorcerer casts Counterspell. The Wizard cannot Counterspell the sorcerer's Counterspell. On her turn, the sorcerer casts Fireball. The wizard casts Counterspell. The sorcerer cannot Counterspell the wizards's counterspell, because her reaction is already used up for the round.