Harpoon?
One Mk 48 more like it. You need at least 4-6 Harpoon for a Sov.
Roger that. A single Harpoon would cause damage but certainly not sink this vessel. Unless you managed some spectacular secondaries and fires.
A Mk48 under the keel would do the trick nicely.
One of the best counters to this ship in the Straits of Taiwan is the Taiwanese diesel-electric boats and other unnamed undersea assets.
You're probably right; only 215 lbs. of high explosive in the warhead.