Hello,
One thing you have to remember is that you are not actually "charging a deposit". The security deposit does not mean a guest will be charged that fee. There is simply a hold on their credit card should there be any damages that you need to claim for. If you are concered that putting a secuirty deposit on your listing is going to decrease inquries,then perhaps explaining it on your listing description would help any confused guests.
Now, sine you have expereinced some damage from your guest, you need to go to the Resolution Centre and provide a written statement of the damage and upload photos and estimates for the repair. The guest will have 72 hours to respond. If they do not respond or decline your request, you have the option of having a Case Manager review your case and decide. But please remember to provide sufficent evidence and description of the damage.
Good luck and keep us posted! 🙂