Should he be institutionalized?

He is not going to kill himself, he's bluffing (studies show that serious people don't tell anyone because they'll try to stop them). Did he become blind recently, or has it been a while? You can't enable people like this, tough love is best. You should stop cooking for him, believe me, he'll do something then. Your mother should tell him that if he doesn't go to weekly therapy and take his medications, she'll kick him out, and he will have to go sign up for disability (unless he already has it, in which case they'll give him housing anyway). You could commit him since he's threatening suicide (they'll let him out fairly quick though if they think he's not serious, depending on insurance) but your mom is letting him manipulate her, and if she wants him to get any kind of life, she'll stand firm. Good luck.