Well I just have this ideas

The bum puts the blue box inside of a paper BAG. Where does Betty found the blue box? into her purse that is a kind of BAG, doesn´t it?

Q: How many time does Dan see the bum? A:"3times". And what happen at the third time?
The Cowboy told Adam that if he see him again once (2 times) he will be just fine, but if he see him twice (3 times)there will be some kind of problems... Is this a coincidence?

Adam drops PINK paint into the jewerly of his wife, any concidence between this and the Pink's restaurant?

Maybe this doesn't solve anything but I think is interesting

I really really like observation #2.

Dan sees the bum 3 times and then dies. The Cowboy shows up in front of the bed of the blonde in bed once to wake her up, and then one more time to find her dead. Does this imply a connection between the dreaming Dan and the sleeping blonde that becomes the corpse?

I like observation #2 also. Basically Cowboy's telling him that something bad will happen if he sees him for a third time. The third time Dan sees the bum he collapses and possibly dies.

Dorothy (in the Wizard of Oz) clicks her heels 3 times to leave her dream and return to reality (home). Does the cowboy signify leaving the dream...a dream that our dreamer doesn't want to leave...and returning to reality? When he visits Adam, it is with blue lightening type flashes. We see these same flashes at the club, and then again when Diane sits on her couch staring at the key. The blue light flashing may be 'the cowboy', and I think it is a sign of waking. Any characters in the dream then cease to exist, and they are normally forgotten (we rarely remember our dreams), which is why we see Diane lifeless on the bed...she 'dies'.

Q: How many time does Dan see the bum? A:"3times". And what happen at the third time?
The Cowboy told Adam that if he see him again once (2 times) he will be just fine, but if he see him twice (3 times)there will be some kind of problems... Is this a coincidence?

I think these scenes, 'Dan and the bum' and 'Adam and Cowboy' are meant to be connected. Not a coincidence. I've seen a lot of people wonder what Cowboy would to do Adam if he did bad...even myself.

What will happen to Adam has already been shown to us through the story of Dan and the bum. It is the act of seeing him that is the punishment.

And this leads me to believe something else. Dan said that he saw a man...not a monster, not a bum, not a scary man...but a man. When Dan saw this man in his dreams, he looked like a normal man. The third time, however... Maybe on the third visit 'the man' revealed his true face. Removed the facade.

In Dan's dreams, it wasn't the appearance of the man that scared him, but rather what the man was doing.

What is the man doing to Adam? Intimidating him. Bullying him. Making him sell himself out in order to have the good life...prostitute himself.