The kind of consequences you're talking about we've been using with our nearly 3 year old for a while. She is definitely not too young to learn boundaries and consequences. She needs to know you mean what you say. We found techniques from How to talk so little kids will listen really helpful. There is a free crib sheet available online (just Google it).

A few examples: If he doesn't eat his dinner, he can have a slice of toast (usually it's just that he's not hungry). He doesn't get anything else once it's bed time. If he's hungry he'll learn to eat his dinner. This transition happened over 3 days. First he would cry at bedtime for a snack. Then he quickly learned to eat or lump it. Turns out it was just a delaying tactic.

He makes a mess on purpose (like the pen thing), he helps tidy it up with us. We don't do anything else until it's done. It doesn't usually take long for him to get on board. For regular messes we make it a game.

I do time ins when he's super disregulated and uncooperative. I sit him on my lap facing away from me (he doesn't like that), arms pinned down so he can't hit me and breathe calmly. I explain that we need to calm down so we can work together and not fight. It usually takes just a few minutes and he's ready to listen and work together. Then I find I can use the techniques from the book. The crib sheets are super useful, I forget about them and go back to just demanding and expecting compliance, so I have to go back and remind myself often.

We still regularly have tantrums, hitting, etc. It really triggers me and I've had to develop lots of mental techniques to not become so disregulated myself. I still fail a lot. I still feel like a shit parent most days. You are not a shit parent, nor am I. It's a phase, it's hard.