Please reconsider your possible strategies and retain a bankruptcy attorney with specific experience with the Trustee in question and in the court hearing your case. You cannot "force a dismissal" but you are about to do something foolish and regrettable. First of all, dismissal is not at all what you want. You want your case to be closed. Do not proceed without competent advice. If you think an attorney is expensive, just wait until you learn the cost of ignorance.
Again, best wishes for a favorable outcome, and please remember to designate a best answer.
This answer is offered as a public service for general information only and may not be relied upon as legal advice.
The only way to move this case along either toward closing of the case or toward a dismissal is to file a Motion either to dismiss your case or to force the trustee to abandon his interest in estate property. You really need to discuss your case with competent local counsel, even if it cost you some money.
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No, you can't get from here to there by sending a letter, not a formal pleading.
Particularly if you think something nefarious is going on, why send a letter which can be 'lost'; better to file a motion to have something. And as counsel point out, you want closure not dismissal. And who says this case is a No Asset case? As pointed out, a competent attorney can guide and counsel you. I concur with the advise offered to you.
This is general legal information, not intended to apply to your specific case. And I may not be licensed to practice in your particular state. Under Federal Law, I am a debt relief agent.