Well first of all, it will surely be more than $818 now, they will have added late fees, jacked the interest rate, overlimit fees and etc.
Plus if they are pursuing it through collections they will add fees for that and fees for the court filings, so you can expect it to just get bigger.
The settlement conference is just that, before they do an actual suit, they want to meet you with to see if you can settle this amicable so they can get the money that you owe them. They will want information about your income, finances, assets and etc.
You do not have to go, but if you don't, expect the lawsuit to be filed immediately and expect to be compelled to provide that information by the courts.
Wether or not your husband can be held responsible would, I think, depend on if you are in a community property state, I am not sure if Ohio is or not, but I am sure someone will pop in to tell me if I am wrong or if he will be responsible and etc.
If you don't go to the settlement conference, as I said they will file the law suit. If you don't attend that hearing, they will get a default judgment against you. Yes, your SSDI is safe, however, that will not stop them from putting a lien on your bank account to take whatever money is put in there. Then you will have to fight with them to prove it is exempt monies and fight to get it back from them. You can expect a protracted battle there, as once they get their hands on it, they don't like to have to give it up again.
Judgments also have the nasty habit of hanging around for a long time and are often renewable, so if they get one and can't get any money from you now, they can just sit and wait until you do get something worth taking to recoup their loss.
The statute of limitations for a written contract, which is what most judges in the US are treating credit cards as, since you sign for the purchases is 15 years, so I am assuming you are still well within the time frame for them to sue you. A judgment would be good for 21 years and renewable for additional 5 year periods.
You may be judgment proof if Ohio isn't a community property state, but you can expect your credit to be totally messed up, and they will never stop wanting their money, plus they will continue to add fees and interest, so you can expect the amount to continue to grow. They will also flood you with calls and letters to try to intimidate you into paying it.
You may want to attend this conference to see if you can come up with a payment agreement that you can afford so you can avoid the lawsuit and other problems it may result in.