True. I ran a stanley knife down the edges of the moulding on my airlocks (and my mates) to remove the sharp bit that sticks out, it should seal much better then.
Everything sounds fine apart from the no bubbles thing so don't stress too much! Your temp sounds fine as well.
If the yeast gets too cold it will basically just slow down and ferment less vigorously and eventually go dormant (ie less than 5 deg), if it gets too warm it will ferment a lot quicker but begins to make nasty flavours in your beer and will eventually die if you go too far over ~30 degrees. Just think which is better - a slow boring ferment that gives you the best tasting beer with the ingredients you have, or an exciting fast ferment that gives you beer that tastes like ar$e?
Give the fermenter lid a little bit of a tighten just to make sure its good and before your next brew smooth those edges off the moulding on your airlock.