If the business is dissolved, there is no reason to file for a business bankruptcy. If there is no business, there is no way to collect against the business. If the business has assets, you will want to look at filing a business Chap 7 and liquidate the assets. If you wanted to continue the business, I would advise you to look into filing a Chap 11 bankruptcy.
Since you personally guaranteed the loan, they can still collect from you. You probably want to look at filing a personal bankruptcy. You should consult a local attorney to determine which chapter bankruptcy best fits your situation. The attorney should look at your debts and assets and be able to assist you.
It sounds like you already have an attorney to try and negotiate with the Creditor.