Well the fact you want a demonic cane for a scion of a demon suggests to me one of the item of power's powers should be mark of power. Plus it seems pretty silly to be a scion of a demon and not have that anyway. You're concept is "getting out from under his father's thumb," after all. Here's how I'd build him.
High Concept: Kemmlerite Bastard of a Demon Lord
Trouble: Under My Father's Thumb
Powers:
[-3] Evocation (Spirit Power +1)
[-3] Thaumaturgy (Necromancy Control +1)
[-2] Kemmlerian Necromancy
[+2] Demonic Pimp Cane;
[-1] Law Breaker (Fifth Law)
[-1] Marked by Power
[-1] Demonic Copilot
Skills:
Superb: Conviction, Discipline
Great: Lore, Deceit
Good: Endurance, Presence
Fair: Alertness, Athletics, Indimidation
Average: Weapons, Guns, Contacts, Resources, Burglary
Focus Items:
Silver Coin (+2 Necromancy control, +2 offensive spirit power)
Rotes:
Spirit Shield- Block 5- one mental stress
Death Bolt- Weapon 6 (tied to Silver Coin)- no mental stress
Soul Steal- Weapon 9 (tied to Silver Coin)- two mental stress
Gate to Hell- Weapon 12 (tied to Silver Coin, Demonic Co-Pilot)- 2 fallout, 4 mental stress