"A fellow almost damn'd in a fair wife."
The attempts made to give sense to 'wife' here are utterly ridiculous. I cannot see any objection to life, the reading of the sagacious Tyrwhitt. Here, as elsewhere, it may be observed 'damn'd' is merely to be damned, i.e. condemned, be odious, as a person of fair regular life must be in the eyes of an Iago, who in fact says of Cassio's (v. 1) "He hath a daily beauty in his life, That makes me ugly." If the allusion be to the person of Cassio, we might read face, skin, or some such word, as denoting effeminacy.
"Plague him with flies. Though that his joy be joy."
Perhaps the second 'joy' was suggested by the first instead of high, bright, or some other adjective.
Sc. 2.
"Abus'd her youth with drugs or minerals
That weaken motion."
I read with Hanmer waken, for that was the object of philtres. 'Motion' is emotion, desire. In the next scene we have "To cool our raging motions, our carnal stings," and "mixtures powerful o'er the blood."