fermentation seems slow

Hi, I'm brewing my first batch of beer. I'm brewing an irish red ale. It's been seven days and i took a barometer ready that was 1.021. The airlock stopped bubbling after 3 days. I am wondering if my beer seems to be on course to complete fermentation at 1.010 or if fermentation has stopped prematurely. I used Windsor ale yeast. I have it in a room in my basement with a space heater keeping it warm. The space heater has a temp setting I've kept it steady at 70, however, due to blown fuses the temp has not really been very steady. is my beer going to keep tormenting over the next week and how do I tell other than taking a barometer ready?

you need to take two hydrometer readings over a space of time in order to be able to determine if fermentation has infact stopped. though, unless you suspect a stuck fermentation for some reason which would require your intervention, you dont have to keep track that much. just give it the right amount of time and it will finish on its own. theres nothing much you can do about the fermentation at this point anyway, its on its own now.

remember that a bubbling airlock means that fermentation is happening, but a non-bubbling airlock doesnt necessarily mean that its not fermenting.

if you plan on secondary-ing the beer, i would wait untill day 7 to 10 and rack to secondary. then just leave it in there for 2 weeks to finish. if you arent using a secondary, i would give it a full 14+ days in primary just to make sure its done. after you take a post-boil gravity reading, you really dont need to do it again unless you want the data for your notes or to determine an approx %ABV.

i know its hard to have patience on the first time, but that is the best thing for the beer.