Well, if the questions are unclear, it is usually best to ask clarifying comments and/or flag/vote-to-close as unclear (we have a close reason dedicated just to that issue). Flagging it as "Should be closed" will put it into the review queue and more experienced members can decide if it should or should not be closed.
In some of your example questions, the best answer seems to be writing the equation and/or definition and explaining each term in it. For example, "this is the time rate of change term, this is the flux term, this is the body force term, etc." with examples of what each of those signifies physically.
Overall, I would say you're doing things correctly. You are asking clarifying questions in the comments when things are unclear. The only next step I would take is to flag the question for closing if you think it is too broad, based on opinion, more about philosophy than physics, or if it is still unclear and the original person has not clarified or refused to clarify. More senior members will decide and you can check back periodically to see if they agreed with you or not. It's the best way to cut your teeth on learning the policies of the site.