Advice needed regarding a Stout Druid becoming a werewolf. (Also, help with CR?)

[Arkhios]

In a game I run, there's this one NPC that's based on a character from another game who is converted to be a Stout Halfling Druid of the Moon Circle.

How should I modify the werewolf stat block considering that a halfling is small.

Should I change the hit die from d8 to d6?
Does shapechange from Halfling to Hybrid Werewolf change size from small to medium?
Which racial traits a Stout halfling werewolf might have?

The character/NPC is likely a 9th level spellcaster using druid's spell-list. How would that change the statistics?

Pre-determined stats are Str 15, Dex 14, Con 16, Int 8, Wis 18, Cha 13, including the ASI's from being at least 9th level druid.

Here's the stat block for the resultant NPC / Monster, and I could use some help with calculating the Challenge Rating.
Homebrewery Stat Block (http://homebrewery.naturalcrit.com/share/r1E0PwiTg)

I came up with an average CR of 6, but I'm unsure if I took everything into consideration

[Saiga]

At the very least, I know that Werebears becomes large in their hybrid form, so I would say that Lycanthropes definitely increase in size when they shapeshift if necessary.

[Arkhios]

Reading further about lycanthropes, I came to the conclusion that since Werewolf doesn't say anything about changing sizes, a halfling werewolf remains small in its humanoid and even in hybrid forms, but when it takes the wolf form, the size changes accordingly.

I updated the OP with the stat block for the resultant NPC / Monster, and I could use some help with calculating the Challenge Rating.

[Saiga]

Looking at the actual wording of the MM, it does sound like you're right. However, since the stat blocks are written with the assumption that the Lycanthrope is a human base, the abilities may not have been intended to imply small or tiny races would stay that size. I think it'd be fair to call it either way, but I would lean toward changing size.

Also, the MM specifies that the creature gains the lycanthrope's speeds in nonhuman form, so it's also up for interpretation if the hybrid form should have a 30ft speed.

[Arkhios]

Also, the MM specifies that the creature gains the lycanthrope's speeds in nonhuman form, so it's also up for interpretation if the hybrid form should have a 30ft speed.
It's only 5 feet difference so I guess I could just give the 30 feet in normal and hybrid form and leave it at that. Shouldn't break anything.

[DragonSorcererX]

In a game I run, there's this one NPC that's based on a character from another game who is converted to be a Stout Halfling Druid of the Moon Circle.

How should I modify the werewolf stat block considering that a halfling is small.

Should I change the hit die from d8 to d6?
Does shapechange from Halfling to Hybrid Werewolf change size from small to medium?
Which racial traits a Stout halfling werewolf might have?

The character/NPC is likely a 9th level spellcaster using druid's spell-list. How would that change the statistics?

Pre-determined stats are Str 15, Dex 14, Con 16, Int 8, Wis 18, Cha 13, including the ASI's from being at least 9th level druid.

Here's the stat block for the resultant NPC / Monster, and I could use some help with calculating the Challenge Rating.
Homebrewery Stat Block (http://homebrewery.naturalcrit.com/share/r1E0PwiTg)

I came up with an average CR of 6, but I'm unsure if I took everything into consideration

If you look on the Monster Manual, most monsters that change size (like an Oni) keep their normal statistcs except that they count as a creature of the size they shapechanged into.

[Arkhios]

If you look on the Monster Manual, most monsters that change size (like an Oni) keep their normal statistcs except that they count as a creature of the size they shapechanged into.

Well, yes, but as written, werewolf polymorphing to the hybrid form doesn't say anything about changing size. Werebear does say, because it's unique for their type, not an universal thing about all lycanthropes.

[Laserlight]

Reading further about lycanthropes, I came to the conclusion that since Werewolf doesn't say anything about changing sizes, a halfling werewolf remains small in its humanoid and even in hybrid forms.

Halfling + Werewolf = Were-labrador. Its attack is a 5ft range Charm spell: You Haven't Fed Me For Hours But I'm Not Angry, Just Terribly Terribly Hurt.