Due to the short half-life of Ativan, you are more likely to sense symptoms quickly. 0.5mg Ativan is equivalent to 3.8-5mg of Valium. A cut of 0.5mg to 0.35mg is almost 50%- In my opinion and based on the experience of others posted here, that's way too much. Probably explains your severe symptoms.
If you could convert to Valium, the long lasting half-life may help. Flush free niacin and buffered vitamin C can help relieve some symptoms. Good luck.