Whelp, $150 and a 2 1/2 hr round trip later she's back on the road. I'd say if you plan to do a leak off test it *could* be prudent to just replace the whole line assembly with the new SS fittings while you're in there, or at least have the assembly on hand. It can be had for $40-$60 shipped.
The p/n on the bag I got from the dealer was 6120703832
I didn't even put very much pressure on the one that I took off that broke, so if you do a leak off test and have the plastic return fittings I'd suggest not exerting ANY pressure on the barb arm of the tee.
The good news out of all of this is that none of my injectors leaked off more than about 3/8" of fuel into the 3/8" line, and they're very likely original and have about 280k miles. I know this doesn't mean they're for certain all good, but it's some peace of mind.
Thank you all once again for all of your help