First homebrew: Scurvy Cure IPA

Take another reading in 3 days. If it hasn't changed, attenuation is done. Also taste the next gravity sample for off-flavors. Most beers benefit from some extra time in the fermenter before packaging.

BTW, how did you measure that fermentation temp? It would be very unusual for it the beer/wort to stay at one temp throughout fermentation (without some type of control).

Underpitching isn't necessarily a death sentence for your beer. There are some problems that can be caused by very low pitch rates, but that doesn't mean they always will. There are multiple variables that affect each one.

 

Sounds like you're in good shape.
Don't worry too much about yeast pitching rates right now - obviously it's far too late to worry about it.
Next time, consider a starter, but plenty of people have made perfectly fine beer by using just what is provided in the packs, be it smack pack, vial or dry.
Also, don't go solely by the bubbling of the airlock to gauge how fermentation is going - as long as it looks like something is going on in there, things are going well. If you're at a couple days post-pitch, and there is nothing - no krausen (foam) no bubbling, anything, then it may be time to worry a bit, but like I said, as long as something is going on, everything is happening.
IN this case, I would let it alone for at least another week, Yes, fermentation may be mostly done, but there is still work to be done by the yeast. There may be off-flavors and compounds that were produced that they will take care of.
The hardest thing to learn about brewing is patience. There is nothing to be gained by rushing things along, and possibly quite a lot to be gained by waiting.
You also could be better off next time by fermenting a bit cooler, I like to keep things about in the mid-60s, but you're still within the range of good things happening.