well,first you have to be really close to eachother for it to match you(in terms of points) and unless the server is 60 days old it only searches for matches with those from your own server

in ranked it usually is like that(especially after 2.0)
also i think that the higher your rank goes the more strict the matchmaking gets since after i reached jonin myself i had more or less zero matches(before it went cross server and i got owned by guys with bee hashi sage naruto teams :D)

also me and my friend are both chunin
no idea then :D