If every star had 9 planets like Jupiter, would this account for the missing mass in the universe?

Not by a long shot.

Even this many Jupiters around each and every star would only affect the total mass by about the ratio of the total planetary mass per star compared to the mass of the Sun. For example, the mass of 1 jupiter is about 0.001 times the mass of the Sun, so 10 Jupiters would be about 0.01 solar masses and so this would increase the luminous mass of the universe by about 1 percent. This is a long way from the perhaps 99 percent that some cosmologists would like to find out there! Most of this seems to be in Dark Matter and Energy, and no one has any idea what forms these might take.

Copyright 1997 Dr. Sten Odenwald