The amount of decoupling (pace : heart rate) is pretty low, and the slight elevation could even account for a bit of that, I think. So, yes, given that you were able to sustain that pace for an hour, it seems that your aerobic threshold (AeT) heart rate is probably not lower than ~145bpm. It might be higher, but there’s no downside to being conservative and targeting a lower heart rate.
It looks like you ran this at a 9:30 min/mi pace. You might see some improvement and grab low-hanging fruit by running 20 miles per week at 10min/mi or <145bpm for a few months. A hard run (anaerobic threshold field test) won’t hurt and might give you useful information; it also won’t be as helpful as more time at lower intensities.