I like the concept.
I would get rid of all the creatures that have a conditional "can't be blocked" like intimidate, landwalk, skulk. And then all those cards dealing with changing land types should go too.
Stick with just creatures that can never be blocked. And then pump those creatures and give them
lifelink.
Slither Blade should be in the main.
I like
Mark of the Vampire. Maybe some
Cartouche of Ambition as well.
I like Sinister Posession and
Sensory Deprivation for removal of small creatures. Maybe some
Murder to deal with larger creatures.
I suggest more
counterspell, maybe
Essence Scatter and/or
Mana Leak.
Happy Brewing