Hi.
I have 2 kids and have worked with them for 10 years. I am in no way an expert but the only adviceI can give you is that this is normal, he is, you are and you're doing a great job.
trust yourself, you know what you expect of him and what he's capable of.
Stick to your guns. Your house, you're the adult and you are in charge.
Lastly, choose your battles. Decide what's important to you. I've always let my kids choose their own clothes, decide bath or shower, peas or sweet corn etc but some things I won't budge on. They will speak when spoken to and they will help with manageable jobs around the house and they will use manners. These things are all entirely down to you choosing what's important.
If he wants to wear mismatched clothes (or very little) let him (he will be cold and then you can offer him trousers, jumper etc)
Don't fret. Things get easier, promise. Xx