If your husband was the sole member of the LLC during its entire existence, and he did not make an election for the LLC to be taxed as a corporation, then it has always been a "disregarded entity" for federal income tax purposes. As such, there has never been a separate federal filing requirement and accordingly there are no penalties associated with having failed to file a return. Rather, any deductible expenses he may have incurred in setting up and operating the LLC should have been reported directly on his personal income tax return. He could go back and amend those old returns, but the 3-year statute of limitations will likely prevent him from claiming any refund.
I'm afraid I'm not familiar with the procedures or penalties associated with dissolving the LLC in Nevada. If the State is not badgering you about doing so, however, you might consider letting that sleeping dog lie. For federal income tax purposes, however, it would not appear there is anything that you need do at all at this point.
Please note that there may be other issues to consider in this matter, however. For example, if your husband contributed any cash or property to the LLC when it was organized, then he cannot withdraw that cash or property from the LLC if it owes any taxes or fees to Nevada, at least not without becoming personally liable for those taxes and fees. You should sit down with a tax attorney or an accountant to examine the books of the LLC to see if there is any possibility of that.