Herding breeds are often tough... so you have a mix of 2 dogs that need a ton of exercise. Doing a lot of obedience work also will help keep his mind busy. A tired dog ... both physically and mentally, is a good dog (or at least a much better one ).
This site has a lot of lessons (on the left side ) and troubleshooting (on the right) http://www.clickerlessons.com/index.htm
Skittishness often is something that must be watched and worked with. A dog that is fearful is more dangerous than one that is simply aggressive. Doing confidence building, but also a Nothing In Life Is Free to help him understand he doesn't get to guard or protect you... that he is not in charge, should help a lot. Unfortunately, dog to dog aggression can be a serious issue and you may need professional help as, at a year, that is only likely to intensify as he matures.
http://k9deb.com/nilif.htm