Well, let's boost the base creature HD to 5 just because we have an excuse for another change. We could potentially modify an ability score or two --- it's justifiable but not necessary from Kelemvor. What do you think?
That seems pretty good to me, and I was in fact thinking something along those lines myself.
Those two skills work well. It is a panther, after all.
Weapon Focus for the feat, I think.
Let's go with regen 3.
Had a thought: how about we give them a racial penalty to Control Shape checks? Or force them to make involuntary change checks after losing a smaller fraction of their hp? Flavor-wise, I think that goes along with Kelemvor a bit.
I'll have to go flip through the adventures tonight. IIRC, there's an important point where he does involuntarily transform (maybe more than once), but I'm not sure if the trigger is always his specific "no altruism" curse or if there's a lunar component. But I like your idea. We could say that each werepanther has a distinct trigger and list some examples (or make a random table).