Pretty much what SG says. Add 2 additional runs in at 5m each and run them slow. You are already getting your speed sessions in but you are neglecting your endurance side. dont be tempted to run the additional sessions fast....nice and slow.
oh...and maybe buy 5 apples and get some oranges with whatever change you have left.
Reasonably often. Not every week all yr but for an 10 week training plan for a 5k there would be a over volume session in once a week. It's hard work but sometimes that's not a bad thing. Some sessions should be hard work and have you struggling.