You should file your tax return as Married Filing Jointly. You being self-employed and your spouse receiving Social Security benefits does not prevent you from filing jointly.
To complete and file a 2018 tax return using TurboTax you would need to purchase, download and install on a personal computer one of the 2018 desktop editions from this website - https://turbotax.intuit.com/personal-taxes/past-years-products/
A 2018 tax return can only be printed and mailed, it cannot be e-filed.
The question is rather to your spouse, should he sign a joint return? When a spouse signs a joint return, they take legal and financial responsibility for all the facts, figures and tax owed. Sometimes, a person might not want to be responsible for the mistakes or problems of their spouse. If your spouse refuses to sign, then you have to file MFS.
Assuming your spouse is not worried about liability, then it is almost always better to file MFJ, even if one spouse has no taxable income. The tax rates are lower for MFJ and many deductions and credits are reduced or disallowed for MFS. Also, if you file MFS, then your spouse's social security is automatically taxed at the maximum rate and your spouse must file a tax return. If you file jointly, your spouse's social security might only be partly or not taxable, depending on your other income.
Hopefully you made estimated payments. Your penalties are a percentage of the amount of tax you owe, so if your estimated payments are more than your tax and you are due a refund, then you won't be assessed a penalty at all. If you do owe tax, Turbotax may offer to calculate your penalty and add it to your tax bill. I would decline this if you can, and wait for the IRS to send you a penalty assessment. If this is the first time you have owed a penalty, you can request a one-time penalty abatement. (Interest on the late payment can't be abated but it may be less after recalculating it without the penalty included.)
To file a 2018 return, you need to purchase the 2018 Turbotax program to download and install on your own computer. The online web site can only do current season (2019) returns.