Robob,
If you really don't hear any mistracking on high pitched tracks, (it seems that your alignment is OK & so in terms of phonostage overload) but you do hear sibilance & grunge, I suggest you, after you get your new arm, to examinate your cable loom : (clean highs, refined mids, but full of body with strong foundation & soundstage completeness).
Overall the problem seems to be a synergy thing : TONALITY
IMHO you need a more capable arm & more sophisticated cables to find calmness & effortless flow & do some experiments with platter MAT.
If you really don't hear any mistracking on high pitched tracks, (it seems that your alignment is OK & so in terms of phonostage overload) but you do hear sibilance & grunge, I suggest you, after you get your new arm, to examinate your cable loom : (clean highs, refined mids, but full of body with strong foundation & soundstage completeness).
Overall the problem seems to be a synergy thing : TONALITY
IMHO you need a more capable arm & more sophisticated cables to find calmness & effortless flow & do some experiments with platter MAT.