Hi,
It always saddens me to hear of a child that has to grow up with diabetes, but it also is so lovely to see how parents like yourself take it in their stride and work so hard to do the best for their child. I know it's especially hard in the beginning, with so much to learn it can feel very overwhelming, but it looks like he's in good hands.
In regards to hypo's adults and children tend to have different warning signs, and of course a child will most likely describe how their feeling in a totally different way too.
You will learn how to recognise them for him, i'm 23 years old and my mum can guess where i am from how i look or what mood im in! she's usually on the ball too!
I think you will learn alot from your motherly instinct, from his mood changes, some children can have mood changes which can be a good indicator, grumpiness, giddiness, becoming clingy or tearful.
I've read a few parents struggle in explaining when their child lashes out at another child during a hypo, i think the best way is to explain to child and parent that his behaviour was down to a hypo, but still tell your son that it is wrong to push another child and of course apologise to the other child so all is well with them both. It will be hard because technically it wasn't his fault but will need to learn how to control how a hypo makes him feel. I can get grumpy when i have a swing in blood glucose, most people will know it's down to that, but i always feel terrible for being grumpy and snappy and i always apologise even if the other person is saying don't worry about it.
Keep encouraging him to tell you if he feels funny or poorly, then he can start to associate his own warning signs and be able to tell you or other adults more frequently and as soon as possible.
Most of all best of luck to you and Jac, it will get easier. Diabetes is a pain, i always find it remarkable at how resiliant children are with a thing like diabetes.
Oh, and it won't be long before (if not already) he starts to associate hypo's with sweet things and doesn't see it so bad if he gets a little treat