Most (all?) fermentations have trace amounts of methanol, with the tendency of fruit-based fermentations to have more.
However the amount is so low, it is insignificant - unless your concentrate it. One method of concentration is via heat distillation.
Note: It's not that you're making more methanol by distillation, the process just concentrates the ...
The OSHA standard is an inhalation warning of pure diacetyl in air. You're measuring diacetyl in a liquid. Its very different saftey-wise. As long as you aren't aerosolizing your samples and inhaling it you're fine.
If you are using a simple pot still, you may not get high enough proof to burn on your first run. Without knowing actual volumes and ABVs here it is hard to say what is the case here.
Normally when producing potable spirits, most things are distilled again a second time, or a reflux column of some kind is is used.
If you are running a second distillation ...