To me it sounds like he wants your attention and this is his way of going about it. Maybe you just need to 'trick' him. Before asking him to brush his teeth get him to pick a book that you will read to him after he brushes his teeth. If he doesn't brush them by himself the book doesn't get read. When he does make a big deal of it and read the book (doing all the funny voices )as a reward for doing what you have asked of him. Make it fun and exciting for him so he wants to brush his teeth every night.

As for monstsers, some kids really do believe they exist. Put some Lavendar oil into a spray bottle of water to make monster spray. When he gets scared all he has to do is spray it at the monsters. So maybe spray the bathroom before he goes in there to brush his teeth and his bedroom before he goes to bed etc.