First off, Lead doesn't give off fumes till it reaches 900 degrees, which is much hotter than you will ever be casting at, a lead thermometer or PID will make sure you never reach that temperature. The biggest issue with lead is handling it with bare hands, the oxide / corrosion / dust that forms on the lead's surface gets on your hands and everything you touch, lead isn't absorbed through the skin but rather you ingest it through the mouth or breath in the dust.
Simple precautions such as wearing disposable gloves, not eating drinking or smoking while handling lead or lead based alloys and washing your hands thoroughly with soap and water when you're done. I cast outside when possible or at the doorway of the garage. Casting in an enclosed area that doesn't have some type of fan or hooded fan system to pull air from your work area to the outside is a bad idea as well.
To answer your first question, the Lee 311-93-1R is a good bullet for the 7.62 x 25 it's the bullet my brother uses in his CZ-52, I usually cast his bullets from straight wheel weight alloy and water quench after I powder coat and bake them in the toaster oven. I size his to .309" but yours may be the same or smaller, generally .001 to 002" over groove dia. will work fine.