Step Up basis rule

My late husband and I had an LLC that owned 1 piece of rental property (the LLC was the listed owner, but we were the only people involved with the LLC).  He and I were the only owners and managers of this LLC.  My late husband died in 2018.  I sold the rental property in 2022.  I reported it on taxes using the original purchase price in 2013.  Since it was owned by the LLC, was I able to use the “Step-up basis rule” to use as the adjusted cost basis?  2) If so, I was unaware that I should have gotten the property appraised at his death in 2018,  so can I use the 2018 property tax value as the cost basis, (my state is a community property state and assesses the property taxes at the Fair Market Value)?  3) I am considering filing an amendment to my tax return & understand that I have 3 years from when it was reported on my taxes (April 15, 2023), so I need to decide by April 15, 2026.  Will an amendment such as this most likely cause an audit?   Thank you so much for your assistance.