All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.
It is permissible for a woman to take off her Hijab in front of a blind man provided she is sure that no one else may see her; the evidence is the narration which you mentioned in the question and which was reported by Imaams Muslim and Ahmad .
As regards the narration in which the Prophet ordered Umm Salamah and Maymoonah to observe Hijab in front of Ibn Umm Maktoom then a group of scholars classified this narration as weak.
However, some scholars provided this narration as evidence proving that a woman is prohibited from looking at a non-Mahram man, as the Prophet said to them: "Are both of your blind?" Therefore, the order to wear Hijab in this narration is for this purpose (i.e. forbidding women from looking at non-Mahram men).
As regards the issue of staying in seclusion with a man, then it is not permissible for a woman to stay in seclusion with a non-Mahram man even if he is blind because it is not safe for the woman to be sexually attracted by him and vice-versa, and because there are authentic Prophetic narrations which absolutely forbid a man from staying in seclusion with a non-Mahram woman.
Allaah Knows best.