I'm looking for a word that one could use by itself as one would use "cute" or "adorable" in a sarcastic, emasculating manner.
The use of 'twee' might be evirating
Twee: affectedly or excessively dainty, delicate, cute, or quaint
The term precious is often used in an ironic and derogatory manner
Affectedly dainty or overrefined: precious mannerisms.
I think pretty used for a boy/man or handsome used for a girl/woman.
Describing anyone as delicate is probably done so sarcastically. I would throw in elegant too.
And then unless it is a dad talking about his daughter add in treasure, jewel, gem, little diamond.
She is just such a delicate girl, you must be so proud.
How glorious she is with the little bows in her hair.
He is so little. Look how pretty he is.
And in your specific case: Look at those delicate little calves on his gem of a body. His legs are so elegant, he is so pretty.
Diddy is a version of the word 'little' which is meant to sound like a baby is saying it, or an adult is saying it to a baby in a 'baby voice'.
Did you hurt your diddy little calves?
could be said sarcastically. The expression lickle, ickle or ickle-wickle could be used in a similar way. There is also a word Diddums which means 'little one', is used to refer to a baby, and is almost only ever used sarcastically:
Did you hurt your ickle-wickle calves? Aah, Diddums!