No, you do not need disability insurance if there is no income to replace. Spend the money on good health insurance.
Technically, as you approach ER, you have less and less need for disability insurance.
Before I FIREd, the minimum disability insurance (it was part of my work benefits) that I was allowed to have under our plan was 50% of salary. This was way too much for me -- much more than I spent and way, way more than I needed as I approached FIRE. But there was no way to reduce it, that was the minimum.
Kramer