One thing I think is 8.5lbs is too much for a 1800 lb car. We run 5.5 in our dragster at that weight and I only run 7.0 in my roadster. If you have no traction problems then go with the 8.5. You are on the right track checking the roll out and front end alignment. See what you find there first then look elsewhere.
You might want to check the chassis really good for any broken welds that could move under power also. If the chassis doesn't have enough caster built into it they can be a handful. I've seen it before. Wouldn't affect the launch though.
Curtis