Weighing the opened and bagged powders only helps if you know how much the original package weighed, and you're equipped to do the weighing very accurately. Plus, some of the components in the developer can oxidize just from exposure to air and moisture.
If you want reliablity, it would probably be best to ditch the D-76 and fixer. If you'd like to experiment, then mix them and see what happens.
The hazard of experimenting, especially if you're also a newbee, however, is that you may not be able to determine what failed, if you don't get the results you expect.
That said, the fixer is probably usable, if you can determine how much water is needed to mix it.
Fixer has fewer components, and isn't degraded by oxidation. It's also easy to test, and won't yield ambiguous results.
For the rest of it, I agree with Thomas that the stop, photo-flo, and Dektol are likely fine.