I hope this message finds you well, present circumstances excluded. I am a licensed attorney with over a decade of criminal law experience. It is a pleasure to assist you today.
You should get him to put this in writing that if he is allowed to remove his possessions, then he will dismiss the charges. He can email this to you if that is the most convenient thing. By doing so, if he proceeds forward anyway, you can use this as evidence to cast doubt on his claims against you that he went against his own word. It will be a character questioning detail if he does not do as he has stated.
You should definitely let him get his things with law enforcement present. If this goes to court, you never know how things are going to turn out. By allowing him to do this (especially with a written acknowledgement of his plans to drop the case), you control the dynamic. If you go to court, even if you have a good defense, you do not control the dynamic and it can have life altering consequence. A conviction for domestic violence will make it very hard to get a job, get credit or a loan, etc.
Let me know if you have any other questions.
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Best wishes going forward!