I can't speak to the inventing question as I'm not sure - my understanding is that pregnant sims who have the pregnant moodlet do have some sort of immunity to accidental death if they're in your control, but I haven't been moved to test it myself. However, if she's still in the early stages where she's nauseous from unknown causes, I wouldn't risk not letting her have access to a shower if she's inventing, or having her try to repair something electrical with a puddle in front of it. It's possible the baby may end up with a random trait or two if her needs bars went into the red as a result of electrocution or whatever, regardless of pregnancy stage.
As to your other question, it's the night vigor moodlet that's boosting the skill level, which is a nice perk for vampires. I've never had a pregnant vampire, but from what I can tell I haven't seen a difference between pregnant and non-pregnant sims as far as how fast skills are learned. I doubt learning alchemy will have any effect on the child.
