Assassin's Blade and Tortoise are unusual and only worth anything for you because you're going for Crab which is also unusual - but they make sense if you do want Crab. You'd also want to pick up the extra resist reduction from Murmur/Rumor and with Soulrend's potentially huge Cooldown reduction (with the help of other CDR gear) might want to consider getting Aeon's Hourglass instead of Leviathan so you can have Mirror of Ereoctes or Blade Barrier up almost all the time. Typical skill setup looks more like this: It would be helpful to have more +Shadow Strike too.
You don't really need a default weapon attack with Soulrend so you could go with a Coldstone, Seal of Night, Seal of Resonance, etc. In general your skill points are messed up and you'll have a tough time getting enough DA with other items being standard Spellbreaker fare. In spite of loving Shadow Strike I don't seem to have saved them (I guess because I don't really need them for myself anymore) so you'll have to search around yourself on Crate's official forums if you want them. All sorts of Spellbreaker Shadow Strike builds have been pretty well studied and haven't changed much in a while. Either way you'll end up with leftover physical damage. I don't recall which of those happens first.
You'll have at least two steps of conversion, one for physical -> cold and one for physical -> elemental.
Conversion is a bit more complicated than that unfortunately.
