Never EVER use a “Close ” nipple as it has no integrity UNLESS you opt for a schedule 80 Brass nipple ONLY a stumble bum Billy butt Crack would use a weak all thread nipple on any pressure vessel see ASME section IV Or NBBI
You are better off with a Brass long shank hose bib or boiler cock.
About removing the broken part use an extractor (easy out) Or if your semi skilled in mechanics you can use a hack saw blade and gently cut out the old part being very careful not to cut into the female threads.
Cut in two places about a 1/2″ apart and using an old screw driver cut out the cut section then cave in the threads and you can pick it out.
You should also consider having a tap available in case you have to retap the threads.