I agree with Markxxx, doing this puts the OP and his family at risk of a needless altercation with the neighbor. The landlord could easily tip off the neighbor who ratted him out, even if he’s trying hard not too.
Isn’t this what Crimestoppers is for? Go online, report him. Tell them what you told us, you can hear him through the walls because all he does is shout and he’s not very discreet, doing deals out in the open, as well.
I would consider the elder abuse thing as well, though you never know if she’s a willing participant or, perhaps bullied into presenting as such.