Looking at what you want to do I’d stay away from intervals. I’ve never found them that helpful except for repetitive actions. Spining is the only place I’ve used them in a game.
I would use a task function. The asteroids tutorial although it’s in 2D shows how a task is used. It’s a lot more powerful than a interval and it will let you do your avatar stuff and attacking.
Learning how to use tasks will help you out a lot.
I use tasks in my program to control both movement and AI. You can set up pretty decent AI you just have to think of the rules you want.