I believe that Manfred, in your first example, is offering to drink the health of the women that these knights hold in respect--the women they either have or are courting. Medieval nights and courtly love are nearly synonymous.

In the second example, I believe he's saying that "I adore her like a mistress" he is using the same meaning: like the woman he holds as most beloved, the woman he has courted and would court again. He's trying to be persuasive and explain to these men that he loves Hippolita so very much, but that they're related and never should have married. With great regret, he feels he must divorce her. It will break his hear, but they should part forever. Oh, and by the way, after that's over, he'd like to marry someone young enough to be his daughter. Someone whom the knights have guardianship of. But it's not that there's anything amiss about Manfred. They should trust him absolutely. He really loves his current wife. They should pity him. He's a great guy. etc.