Like the boys said mate the way you have done the front axle is perfect, the 2 little bolts on the bottom of the fork leg tighten up to hold the axle tight, and once they are tightened the axle will not go anywhere, the reason one end of the axle is wider is due to it acting as the axle spacer.
Ya doing a great job brother, the bolts holding the rear chain sprocket on can be replaced with longer ones which then enables you to put nylock nuts on the remaining thread, the nuts will not sit all the way flush but once tight they will not come loose.
When running the engine in allow it to cool for about 20-30 mins after riding before starting again, and don't be shy with the throttle during this period, so wide open throttle is fine but doesn't mean every minute of riding like that during the run in.
