You should hire an attorney, he can present evidence, but he cannot speak as a witness. It is best if you can appear. If your family member is just going to repeat what you told the family member, it is very likely their testimony will not be admitted.
On what the judge will do, that requires more facts and no attorney will claim to know exactly what a judge will do.
Your question has no relation to the facts presented; if you didn't return the security deposit within 30 days (or provide the tenant with a written account of charges you applied to the deposit) then the tenant can sue for 2x the security deposit.
Your other issues are potentially actionable, but have no bearing on whether you may or may not have violated the Rent Security Deposit act.
The foregoing is not legal advice, and nothing in the foregoing shall be deemed to create an attorney client relationship. If you feel you need to speak with an attorney regarding your issue, it is recommended that you contact an attorney with expertise in your area of inquiry. The information related above is purely for informational purposes, and should not be acted upon without speaking with qualified counsel familiar with you specific situation and the laws related thereto.
NJ Statutes require that you return the security deposit within 30 days of vacatur or provide written notification certified mail as to the damages. You may be liable for 2X because you did not provide the tenant with the notice. You cannot have another person represent you. You will have to hire an attorney who can represent you if you cannot appear.