When the option to completely eliminate the problem is available, but one chooses to just reduce it a little further, I don't see that as a moral victory.

There is no option to completely eliminate the problem, unless you are seriously advocating the death or murder of billions. That isn't an exaggeration. Humans must eat to survive. The cultivation of crops is a requirement for the well being of humans. That does not justify or excuse, in any sense, the needless deaths of sentient beings.

This is a little hyperbolic, but I find it a little similar to stating that one murder is more moral than another because he only killed 4 people where as the other person killed 7.

I don't think that is an indefensible view. It is one our justice system recognizes. It also recognizes that the death of a single sentient being is objectionable - we send murderers to jail to prevent the needless death of sentient beings. We don't do everything possible to prevent all such deaths, we instead act to reduce the amount of suffering. We balance considerations about human well being, including human freedom, rights to privacy and the like with the need to prevent crime.

I'd just bring up a cost/benefit analysis here. Keeping in mind that every person on earth would need to stop consuming meat to get that 7%, I don't see it as a very viable strategy.

It might not be, but that isn't an argument against the strategy as a possible asset. It argues against the viability of the strategy. Ultimately global Co2 emissions will need to be 20% of their present value. Should we devote ~half of our global CO2 budget to animal production?

I still see this as a I've decided this life is okay to harm, and this life is not point of view. I don't find a moral difference in the number of beings harmed; They either are harmed or they are not.

It is a decision about what amount of suffering is preferable, but it is not an arbitrary decision. We should prefer the minimal amount of suffering, and not only does the number of people (or animals) suffering matter, but so does the amount of suffering that each experiences.