I won't rant -- that was a lovely letter!But I do want to say: thank you for your service! Your experience will never completely leave you, nor will the friendships and sense of place.
The most important thing to do is take your first step into a decision rather than think away your entire situation without actively doing anything about it. So go visit higher education institutions, get a list of apprenticeships that might interest you, search out charity organisations and see what help you can give, belong to a community garden, go back to army even if you felt you learned a great deal etc etc etc. Doors open when you are involved with the world.