Jim, the risk of weight gain is there with most psych meds, it should be the least of your worries. You will only gain weight if you eat more, not just from taking the pills. Like you've been explained regarding Lamictal, if you up the dose very slowly it has reduced risks. I've been on 250mgs for months or so, and not one issue. You'll have to put a little trust in this doc.
Lamotrigine (Lamictal) seems to be missing from your list. It is weight-neutral, but of course it, too, has a list of possible side effects. In my case, I really liked it as a mood stabilizer, but over time it caused pronounced hand tremors. The big one to watch out for is the risk of a severe and potentially dangerous rash. If Lamotrigine is ramped up very slowly, that risk is greatly diminished.
Good luck!