Energy bar is too soft I'm trying to make a recipe for an energy bar that can keep it's form, doesn't melt in above-average temperature, and doesn't stick to the teeth.

I want to use a minimum amount of ingredients. For nutritional profile I have settled with roasted peanuts and sesame seeds. I use dates to bind them, and coco powder or freeze-dried fruit powder for flavor, for example banana.

I have tried all kinds of date pastes, some are definitely hold form better than others, but the bar still bends in middle under its own weight when holding up it in the air.

What other natural ingredient (no chemical preservatives or sugar powders) I can introduce into the recipe to make the bar dense but soft, and not too gooey?
It sounds like what you need is a powder, you could try a protein powder, or you could use peanut butter powder, which is a good thickener. Chia powder is also a great binder. 

Another option would be a gum like xanthan or guar gum. 

Heat is another option if you aren't baking these already, heat will drive out moisture and help the mix crystallize.