and had a WR250R shock head (same bore different reservoir set up ) fitted by a shock guy , so i only have part of the info , aslo do the same riding as you , it now tracks straight over stuff id normal go round .
No definitive answer so far found on standard oil weight
Lots of useful info in sledman 1's posts on this thread though - http://ttr250.activeboard.com/t49311269/rear-shock-absorber-qa-megathread/?sort=oldestFirst&page=3