[Cdunn]

Can I use a 3/4" PEX x 1/2" Female Threaded Drop Ear Elbow and a galvanized nipple from the valve to to tub spout?

 

[joecaption]

No, for one you would wring off the PEX when trying to get it tight.
I'd also never use a galvinized nipple for this, even though I know most people do because there cheap.
At some point they will all rust out from the inside out and leak.

 

[Cdunn]

My thinking was, pex from valve to a 3/4" PEX x 1/2" Female Threaded Drop Ear Elbow then galvanized to spout. Tighten the threaded fittings, then make pex connections.