After reading what @AmeliesUncle and @tagteam added, it appears you're at a point where you need professional help. This is especially true if your state also taxes personal income, because that's a double-whammy. Looks like the first CPA "said" one thing (27.5 years) yet "did" another (figured on a 40 year ADS instead of the 27.5 year GDS method.) Then when you started using TurboTax you went and changed things yet again in what appears to be an improper manner.
While the TTX program does include the 3115, there is nothing simple about this form. Particularly for y our situation. Bottom line is, you need professional help from a tax professional that will not only do it right, but will show you the fine details of "exactly" what they've done to make it right and ensure you have a complete understanding of everything.
Remember, it's "you" not the tax preparer that signs that statement stating "Under penalties of perjury, I declare that I have examined this return and accompanying schedules and statements,......." Please get professional help.
If the final product will result in a refund for you, then no late penalties will be assessed. So if you "think" you may owe the IRS I would suggest you pay an estimate now, print your receipt and ensure you make the tax professional aware of your payment and provide them a copy of the receipt.
www.irs.gov/payments if you may need to pay 2020 taxes to the IRS.
