So first of reman cyrodiil was an imperial right? Also my main question is what happened when he died, i know that some people worship him throughout cyrodiil, but did he really get some divine power when he died or did he go to dreamsleve or something?

Reman was a Cyrodil, yes.

http://tvtropes.org/pmwiki/pmwiki.php/Main/FisherKing in fact.

He appears to have been hero-worshiped before the ascension of Talos. No word on after, though.