You could but, please keep in mind that everything you mentioned is full of sugar; especially the molasses.
If your plan is to make that mix every day, you may very well end up with one hyper-I-don't-want-to-listen horse. Not to mention sometimes horses high on sugar get nippy and kicky.
Your pellets should not be so dusty that you have to worry about settling dust down; that is not normal for a pelleted feed.
Is it a pelleted feed that is locally made? If so, I would buy a name brand.
It's also possible there are mold spores in the bag and the horse shouldn't be eating it
I have to wonder how many times horses have colicked because they ate feed that was either sour or on the moldy side and the owner had no idea. Feed stores are supposed to sell nothing but fresh, dated feed but I know from personal experience that does not happen.
The feed stores in my county have learned that "The Look" on my face when I storm thru the door means they owe me money for a bad bag of something.
If an explosion of dust comes out of the bag as soon as it's opened, that is bad news for the horse. My nose is in every bag I open, looking for bugs or dust:)