Cleon
Legend
I'd cut out the "A pilfer vine gains a +2 circumstance bonus on Sleight of Hand checks for every vine that it commits to a theft" bit.
Halflings have two arms and they don't get a bonus when swiping stuff with both hands!

If you want to allow a circumstance bonus, maybe have it apply if its grappling a victim with its other vine, since they'd be distracted by their efforts to extricate themselves.
4 hp per vine is probably plenty. Maybe 8 hp per vine for a Medium sized plant.