I'm considering renewing my KVS subscription, but I can't figure out if it has a benefit over what is available elsewhere.

Mrs. GaryD is JMB Diamond, so seems to be eligible for additional JL award seats. The BA and JL sites provide access to award seat inventory.

Is the BA site data, for using "Avios" on JL flights, the same as JL's data for using JMB miles? In other words, does JL hold back some seats for its own members?

The JL site explicitly says that for Diamond members, more inventory is available, for which a phone call is necessary. Can that inventory be accessed with KVS?

We are looking for an award NRT-JFK-NRT on JL F in June. Which level subscription would suffice for a complete search?

If inventory does open up, what mechanism is there for subscribers to learn of it, other than rechecking regularly?

Thanks.