Good points, the only thing I would add is that from my Qi Gong studies the Chinese identify several Dantian in the body (e.g. Upper Dantian, lower Dantian). When people mention Dantian they usually refer to the middle Dantian, which is similar to the Hara.
Yes, but I didn't want to confuse the OP further. The upper and lower dantien aren't usually referred to in JMAs - in JMAs, the tanden is usually in reference to the middle dantien, aka hara.