As you've noticed, yeast will go gangbusters at higher temperatures but that's not always what we want in our flavor profile. I LOVE california ale yeast fermented at about 62 degrees- clean, without esters. Esters are the name of the "fruity" flavors you get in some yeast strains, and in beers fermented at high temperatures. Often, the fruit is reminiscent of bananas. Slow and steady wins the race, in my opinion! A "hot" ferment can also produce fusel alcohols and other nasty flavors. I have a stick on thermometer (like an aquarium themometer) on my fermenters, because I've seen the temperature of the beer in the fermenter be as much as 8 degrees warmer than the air temperature, due to the heat fermentation produces!
One way to get around using two vials of yeast is by making a starter. A little dry extract and a couple of days, and you can easily grow enough yeast to ferment any size batch. In fact, it might not be strictly necessary, but it's recommended to use a starter with any size batch when you use liquid yeast.
No reason to worry when you remove the lid to take your SG readings. Just be sanitary, and try not to sneeze into it! Oh, and don't return your reading to the fermenter. You can take a taste and see how it's coming along. Then pour out what you don't drink. I always sample my wort, and then the beer as it progresses. With time, you can taste a wort and say, "Oh, wow- this is going to be GOOD!"