Question about JMB Award.

I have found availability on a HND-KIX 13:00 flight in July on BA Avios for 2 seats, but i need a third (1 adult, 2 children). I was going to transfer some SPG for the 3rd.

Q1: It looks like I can only book about 3 months ahead of time for domestic flights. Is this correct? Are there any tricks to booking flights?

Q2: Can I book a 8-year old on their own itinerary? ( Book 2 flights with Avios, 1 with JMB ). They'd be flying together, but on a separate ticket.

Q3: Any tricks to guaranteeing getting that specific July flight? What time to they release award availability (Domestically).