String packing is available at any place that sells the washers and bibs. Normaly the string is teflon and works well. The tar impregnated cotton string type works even better but is nasty to work with. 90% of that kind of bib is imported with no parts support so just replace them when they can't be fixed. Regarding the stubborn screw. I know you are a gearhead of sorts so you will find other use for the tool and occasionaly it can realy save the day when getting a screw out is do or die. I don't recall the proper name of the tool offhand but it looks like a FAT screwdriver and works similar to the old "yankee screwdriver/push drill" elementry schools were alowed to use in craft making before lawers put a stop to it. The difference is that instead of pushing,you hold the point firmly in whats left of screw head and wack the butt with a 10 to 16 oz hammer. You will need the stem in a vice or other means of sturdy support.

Thanks for the info about packing. I imagined that the problem with replacement parts is two-fold, really cheap new bibs and no standardization anymore. It is too bad I can't just replace the stem. I have to replace insulation and re-position heat tape to replace the whole thing.

That's an impact driver that you are talking about. The one I have is too big, but I think I can find a smaller one. The larger ones are probably an inch or more in diameter. I was introduced to those when "splitting" motorcycle engine cases. I've got a use for a smaller one in the lab right now too.

Is this kind of hose bib optimal? This is a "globe valve, correct?

I see other styles including ball valves. Is there something that works better that what I have, either easily rebuildable or more durable? I have 5 of these things and at least two more leak at what is probably the packing. I'd like to replace them with the best practical equipment.

ion,I'm not sure if there is much better to be found on most plumbing isles. You might check a wholesale plumbing house for 3/4 mpt boiler drains for commercial water systems. Without question,there are ball valves desighned for hydraluics that are of high quility. I'm not sure how commonly pipe threads are used on them but if you find them,a 3/4 npt x 3/4 hose thread fitting is available everywhere plumbing is sold.
The packing string works real well and lasts a long time.