I had a an OG of 1.050 and a FG of 1.012. Would that mean I have an ABV of 3.8%.

I think you are closer to 4.9%. There are a couple ways to calculate, but I use the formula of OG-FG times .129. So for this its 50-12=38 x .129=4.9%.

No. You’ll be around 4.9% or 5%.
(OG - FG) * 131ish will equal ABV.

Your 3.8% will be the alcohol by weight…ABW.

Does 5% sound right for a British Pale ale?

Oh yeah, thanks for turning me on to that calculation.