I never assumed you were making a rogue.
But if you're going to emulate the shadowdancer PrC you're going to need at least 16 levels of rogue for the imp. Evasion, Defensive roll and Slippery mind. Which means you have 4 levels to play around with. Dragonmarks, for good or ill, can be affected by metamagics. Trying to fit in a spellcasting class to take advantage of extend spell feat works to your advantage here. Chances are we'll never see any enhancements/items that affect dragonmarks.
(Dragonmarks don't help dwarves so the enhancement dev pretends they don't exist.)
It sounds like you're trying to use Shadowwalk to emulate the Shadowjump ability. The only problem is that shadowwalk doesn't do a good job emulating shadow jump. It's basically a haste and displace that goes away the minute you attack something. You already have displacement and can sow chaos with invisibility so why not focus on that aspect?