Before answering your question it would be necessary to review the partnership/loan contract. Please feel free to contact me for a free consultation. 408 796-9616
Based solely on your facts as posted, I recommend taking the offer to pay 5K a month for 6 months. They unilaterally offered to change the terms you agreed to just to make it affordable to you. Seems like a good chance to avoid a lawsuit...
Not really possible to give a good answer absent reading the investment/loan document to determine if the LLC is solely liable or whether you were also a party either agreeing to be a co-borrower or possibly a personal guarantor. Your choice will be predicated on the answer to these questions. If you are not liable contractually then you could simply bankrupt the LLC and tell the investor/creditor to pound sand .....or if you personally are on the hook then you may want to take a more conciliatory approach and seek a forbearance greement or possibly an amendment to the loan to allow for more reasonable terms that consider your cash-flow limitations.
My answer is not intended to be giving legal advice and this topic can be a complex area where the advice of a licensed attorney in your State should be obtained. Please click "helpful" or "best answer" if my answer added any value or add a "comment" if you have more info for me to help you get a better answer.