The $44,000 is potentially taxable. More accurately up to 85% of it is potentially taxable. More likely, it will be a lot less.
Tax on Lump sum social security payments (including SSDI) are calculated under a special formula that treats the income as if it had been received in the years designated (2016, 2017 and 2018 in your case). So, chances are the tax will be low or even 0, if you had little or no other income*, in those years. TurboTax (TT) can handle the SSDI lump sum calculation. Unfortunately, the $6000 attorney fee is not deductible.
I assume the LTD was tax free. If not, there is a 2019 deduction or tax credit for the repayment made in 2019, so that you will not be double taxed.
*Social security only becomes taxable when added to sufficient other income. ISocial security (including SSDI) becomes taxable when your income, including 1/2 your social security, reaches:
Married Filing Jointly(MFJ): $32,000
Single or head of household: $25,000
Married Filing Separately and lived with your spouse at any time during the tax year: $0
