-Solar Flares effect enemy and player ships alike. There is not only the effect of fire starting, but also damage done to the hull by a solar flare. So even automated ships are effected by that. Keep your shields up, it mitigates the effect.
-Ion Storms effect enemy ship as well. You can't see this because you don't have sensors in a nebula, but it does. You'll notice they aren't powering all of their weapons sometimes.. or if you damage their weapons suddenly they reroute what little power they had to boost their shields.
-Fire will burn itself out if left long enough. With level 1 doors, it will definitely spread long before it has a chance to do that.
-The spiders will not always kill a crew member. I think it's 50/50. Nearly every event has multiple outcomes.