IRS sent me a letter charging me a huge fee, over $30,000 plus a penalty and interest. Who is responsible for paying?

I understand that you are caregiver for your husband but this forum isn't the right place for this question, and unless you want more problems you need to get professional guidance from an actual tax attorney, in person.

Retired IRS tax collector here, answering your question. You are responsible for paying it all. You have a separate issue trying to get a preparer to pay for any part of the various penalties or interest. Do you have any written agreement about his responsibilities? Also, not clear about what those missing papers might be. Did you not give him everything? Did he not submit everything? Is there info that could change the tax assessment so you could request the IRS to consider to recalculate what is due? Whatever the case is, don't delay in responding to the IRS...
the penalties and interest continue to accrue and you could expect to have enforcement action taken to collect the debt. And why is this question on this forum anyhow?

If the guy who did the taxes is a CPA, it's pretty standard for them to represent you in any cases with the IRS. If he made mistakes, then I would think the penalty would be on him to pay.

You may need to consult a tax attorney, though. Many times the penalties can be negotiated down, and if the tax preparer isn't doing his due diligence, you'll need assistance with that mess.