Quibble: GWM isn't a "free bonus action", it's just a regular bonus action attack.
There's a "free object interaction".Is there even such a thing as a free action in 5th?
2. The monk never seems to miss, always gets three attacks a round, and can roam around and attack any enemy he wants with those attacks. For some reason monks get back all KI points in a half hour (not a short rest) so the monk rarely has no KI to spend in an encounter. Doesn't hit as hard as the paladin, though.
I just had a quick scan of monsters in the MM from CR10 upwards. I can't really find one with less than AC17 and many have 18 and 19. A 10th level PC has about +8/+9 to hit. It seems to scale just fine to me. Seems pretty similar to the AC of an average PC, except for a shield user (and many of these monsters could use a shield if they want to I guess)
This is incorrect. The rogue's turn ends when the next creature's turn begins, and since Sneak Attack is per turn, the rogue may use SA once on each other creature's turns.5. Remember that turns are individualized. When combat returns to the top of the turn order the rogue still may be in their specific turn. Rogues seem to think SA damage applies on opportunity attacked but they do not if they expended their SA during their action attacks.
Quibble. The Monk still needs to spend a full short rest in order to get his Ki points back. However, during that short rest, he must spend at least 30 minutes meditating:
PHB page 78:
"When you spend a ki point, it is unavailable until you finish a short or long rest, at the end of which you draw all of your expended ki back into yourself. You must spend at least 30 minutes of the rest meditating to regain your ki points."
(Since there are a number of things you can be doing during a short rest, not all of which would be considered meditating.)