It sounds like he has some fear issues and is also getting a bit confused about the territory he is trying to protect. Problems like this are fairly common in early adulthood so don't feel too bad.
I would start with dealing with his barking at other dogs and people on walks as a fear response. There are a few threads on this that will help you. It is really important you take control in these situations and he knows you will take control (so he feels secure). For the first week or two of dealing with this as soon as he starts going off turn around and walk quickly in the opposite direction, not saying anything. You can turn back once he has calmed down. Once he has the idea you are in control you can use techniques. Work out his 'critical distance' (the distance he is comfortable being near another or person) and try to keep at that distance as you start training, and slowly reduce the distance as he responds to training. You can reward him as you go past (as long as he stays calm) - treats or a toy - this provides a distraction and turns walking past into a positive experience. You can also try obedience commands to get him to focus on you.
You might also it useful to get hold of books an dealing with shy/timid dogs as they focus on a lot of techniques for developing confidence.
Barking at kids going past your place is a really common problem with most dogs - its usually a territorial issue. I would suggest trying to break the cycle first and not giving him the chance to bark at everyone going past (I tend to bring my dogs inside when school breaks up). Calming techniques are a good idea to bring his adrenalin down when he gets excited. You can teach him to come inside when there is some 'territorial' issue - this is what I do with Deska.
Good luck.
