Bathtub Spigot Pipe Rusted to the Elbow

Hi there!

I have a bathtub spigot pipe that broke in my hands as I tried to replace a leaky bathtub spout. The pipe has been rusted all the way to the elbow which is inside the wall. I went into the access panel and saw that the from the elbow the pipe goes up to what looks like a copper 4 way fitting branching to a shower and the hot and cold pipes. I was wondering what I should do in order to get this out. I tried using an ez out and an internal pipe wrench but have hand no success. The next step I was thinking was cut the pipe that attaches to the elbow with a reciprocating saw, pull the rusted pipe out of the backside and unscrew the top half of the pipe. I was also thinking of replacing this all the way to the 4 way junction with copper.

Any help is greatly appreciated! Thank you!
I have attached pictures of the nasty task.

Old, rusted, galvanized connections are often difficult to take apart, even in a vise. Just cut the pipe as you described and replace it back to the valve. I wouldn't bother fabricating a new one in copper. Look how long the old connection lasted. That's just extra work. (Not a pro)