Convert This Villain from D&D 3.5 to GURPS

[Chethrok_Bloodfist]

I'm currently taking a D&D 3.5 campaign I've been planning and changing it to GURPS. So far, the one thing that I'm completely lost on is how to properly balance a fight. The encounter balancing system is one of the strong points of D&D, in GURPS it seems like the only aid is lots of experience (which I don't have).

Any comments or advice will be greatly appreciated!

The Villain: Hardin Issacs, a witch hunter who has been possessed by a powerful demon.

The Design Requirements:
1) He needs to be able to provide a challenging (but not impossible) fight for four 150-point characters in a TL3 fantasy setting.
2) The central ability I have envisioned for him is having long, razor sharp blade limbs erupt out of him to impale the PCs (reminiscent of Kerrigan from StarCraft or Marcus from Underworld 2). This is the one ability he's gotta have.
3) Overall, he should be really tough but slow and not that hard to hit (the demon grants him resilience but his movements are jerky like a marionette's).
5) He should also have some sort of supernatural fear ability or terror effect.

Here's the stats I came up for him under the D&D rules, for those of you who are familiar:

Spoiler:  

Possessed Hardin Issacs – CR 8
CE Medium outsider
Init -2; Senses: Perception +13, blindsight 30ft.
Languages: Common, Dark Speech
AC 18, touch 12, flat-footed 18
HP 109 (8HD)
Fort +13, Ref +4, Will +11
Immune: Mind-affecting spells, poison, disease, sleep
Resist: Resistance to fire 10, acid 10, DR 10/good, DR 5/slashing, SR 15
Speed: 20ft., fly 10ft. (average)
Melee: 1-4 Claws +12 Melee (1d8+4/x3)
Space: 5ft.; Reach: 5ft. (10ft. with claws)
Base Attack: +8; Grapple: +12
Atk Options: Impale
Special Actions: Horrific Gaze, Unholy Blight
Abilities: Str 18, Dex 7, Con 20, Int 20, Wis 21, Cha 20
Feats: Dark Speech (b), Great Fortitude, Improved Toughness
Skills: Bluff +16, Diplomacy +18, Intimidate +16, Knowledge (the dark arts) +16, Knowledge (religion) +16, Perception +13, Sense Motive +16
Possessions: leather armor, wide-brimmed hat

Issacs’ Claws: The possessed Issacs is able to cause long, jointed spears of bone to erupt from his body in a shower of blood and gore. He begins combat with no claws active; each round, he can cause up to 1d2 claws to sprout, to a maximum of four. Issacs can only attack with as many claws as are active, and he can attack with a claw during the round in which he sprouts one. Each claw also has the possibility of impale on a successful hit. Claws count as natural weapons, and can be sundered (each claw has hardness 10 and 5HP).

Impale: Whenever Issacs hits with a claw attack, he may make a grapple check as a free action. Should he win the opposed grapple check, his target is now impaled on Issac’s limb. The impaled creature counts as grappled, with a few exceptions. The creature can still use any weapon, not just a light weapon, and attacks with only a -2 penalty on attack rolls and AC. Issacs, however, does not move into his opponent’s square (he and his target remain at the same distance from one another), and he does not count as grappled in any way. Each round at the beginning of Issacs’ turn, he may choose to maintain the impale or to pull his claw out. Should he maintain the impale, his target takes 1d6 points of damage that round on his turn. Should he choose to pull out, his target takes claw damage (1d8+4) and is released from the impale. If the target is able to escape from the grapple through an opposed grapple check, the target takes 1d6 points of damage as he pulls himself off the claw.

Unholy Blight: In lieu of making claw attacks, Issacs can choose to unleash a wave of unholy energy from his body, affecting everyone within a 30ft. radius spread. Affected subjects each take 2d8 points of unholy damage and must make a Fortitude save (DC 19) or be nauseated for 1 round.

Fear Aura: This aura has a range of 15ft. Enemies who enter the aura must make a Will save (DC 19) or be shaken for 5 rounds. Opponents who pass the Will save are unaffected by the aura for the next 24 hours. This is a mind-affecting fear effect.

Major Questions:

1) How much HP should I give him? I was thinking somewhere in the neighborhood of 25 or 30HP, with DR 1 or 2, is that too much?
2) Should I even bother with a points cost for him, or should I just give him the abilities I want to give him?
3) So far, the best I can come up with for his limbs are Strikers (Impaling, Long x2, Cannot Parry). Any suggestions on how to better represent them?

If anybody feels like actually statting him out, that would be awesome. However, I'll take whatever advice I can get, no matter how general or specific.