Keep in mind that most of what you have read about JAL F is the intercontinental experience, domestic hard product and especially the lounges are vastly inferior and definitely not worth showing up early for (and this is coming from a lounge enjoyer).

If you are swimming in points or passengers of size fine, otherwise for such a short flight I'd sit in Economy for $80 (via JAL Explorer Pass) rather than pay 24k points each way.

In fact HND/CTS terminals have some pretty interesting shops for foreigners and domestic flying in Japan is very civilised, so you may actually not want to feel 'obligated' to use the lounge (to get your money's worth) but rather show up closer to departure and browse some shops while waiting. Service is of course excellent but how much service can one receive in an hour.

Lounge description: https://www.jal.co.jp/jp/en/dom/serv...d/diamond.html
Seat description: https://www.jal.co.jp/jp/en/dom/service/f/seat