Hi Triplets he absolutely loves it. That's what has made it easier for me to get used to it, tbh. He was made for it, I think. When we went to families' day last week it was great to see him interacting with everyone from the others in his troop right up to the Captain and CO. He wasn't awkward or nervous, which he could be before. He had a glowing report when he left, so we're very proud and very pleased for him.
It's very difficult when they first go. It took me along time to get used to him not being here. I had little cries for weeks after he went, then he came home for a long weekend at 7 weeks and it was hard to put him back on the train.
DS1 was so happy when he went, he wasn't at all homesick but was very busy so didn't ring as often as I wanted him to. I didn't tell him that, I knew how busy he would be because DH is in the RAF so I knew how hard the inspections are, but it was very hard to ring him, or text him. They have a lot of inspections of kit, their rooms etc. DS1 had jobs in the barrack block too, on a rota, like cleaning the toilets, showers, corridors, etc, so their days are very, very long and very busy.
It's a double edged sword. On the one hand it's great they don't ring because they are happy and enjoying it, on the other it's hard for us mums because we miss them and want to chat to them. I sent DS1 little parcels of chocolate, nice toiletries, jelly beans, etc (not a lot because they can't store it) because that prompted him to text or phone. Practically every phone call began "Hello mum, sorry I've not rang, I've been busy...." 
I'm sorry I can't help you wrt the leave questions, but what I will say is if you have any questions ring and ask them. They are usually really, really helpful, they'd rather you asked than stewed over it, tbh.
The forces is one big family, the army have looked after DS1 really well since he joined. There was an excellent WRVS facility where he did his Phase2, they had to have that as they had under 18s there. DH and I were very impressed with it. The man in charge of it was really, really lovely, and it was reassuring to see, although DS1 is 20.
Try to keep busy, it makes it a little bit easier and it makes the time go a tiny bit quicker. xxxx
for you and n1cruth