Leave it alone for at least 2 weeks. It is fermenting.
A couple questions and things to think about going forward: Did you use dry yeast? If not, did you make a starter? Was the yeast fresh? Once you start making 5 gallon batches, unless you are using dry yeast, you should always make a starter. At this point, for this batch this doesn't really help or answer your questions, so consider it food for thought.
Regarding the bubbling: The type of lid you have is notorious for not sealing very well. Don't worry about it. Just be aware that it doesn't build up enough pressure to get the bubbler going once fermentation starts slowing, because it is leaking. It will still ferment for a while and it is OK. If you really, really want to see bubbling, seal it with some packing tape. There is still plenty of CO2 on top of the wort and still being generated. When the SG readings are stable over 3 days it is done. But, it wouldn't hurt to leave it for a few days or a week more. For your next batch pick up a lid with a seal gasket. Home Depot sells one for under $2.
Your OG is the value of the completed batch of wort, after you add water and mix it in. You must use this value because that is the volume of the beer you are getting and you need a before and after fermenting gravity reading of the same volume of liquid to get the correct ABV.
More un-solicited advice - When you first add the yeast, you want to get some oxygen into the wort to help get the yeast going. Mix it well - shake your bucket, rock it, bounce it, anything you can do to get oxygen in the wort at the start of fermentation. Oxygen is good at the beginning, but not at the end. Check the OG after mixing well. That is the number you want.
An OG of 1.020 is really, really low. I suspect that it wasn't mixed very well when you took your OG sample (fermenting itself will mix it once it starts). If that's correct, even if it ferments down to 1.005, you would only have a 1.9% beer. Since this is a kit I doubt that is correct. Read the instructions again to make sure you followed them correctly.
if you are using a hydrometer you can compensate for temp as others have said. But, the compensation is only .001 for each 10 degrees or so plus or minus 60 degrees. That's not enough to make much of a difference. Without sounding like a jerk, are you sure you know how to read your hydrometer? Are you converting from brix?
Good luck and welcome to bigger batches. RDWHAHB.
