The article are rather 'old' and there is a reason for this. They hold their weight today and have certainly not been overruled. Compare the few new articles on this topic vs. the older ones, say pre 1960. You find much more information and a break down of paragraphs/passages in the older articles, this I guarantee. Newer articles are exceedingly brief and tend to rush through everything sadly. Again, this I have seen for myself. A class example is World of the Celts, by Simon James. He it states that Gaul was rather well off overall and alludes to the agricultural level and the infrastructure (which is not at all contested by newer or older sources), but here says nothing about the condition of the military, not even a paragraph or a couple sentences. The topic of the Gallic military in the Gallic War seems to be (but is not) taboo among modern authors. You'll be lucky to get more that two sentences about it, that is, detailing the warriors and the overall situation itself against their enemies.. The older ones,despite their 'age,' delve right in and give a great amount of opinions and facts which one surprisingly learns much more.
Maybe, but the problem with the old fellows is that back then source critisicism was not really applied- or in its infancy. And that new interpretations have come forth. I know little of gaul, but if we look at the Danish viking and middle ages where I am an expert (and have myself had no little part in the new understanding), little of what was written 100 years ago has any usefulness. There are many reasons for this and things will get boring if I start rambling. But much has happened in historical scholarship the last century.

If you have access to academic databases like Blackwell, Wiley, and JSTOR, yo can read much on these things.
I do not, I probably could get it, but TBH I am not too keen on Celts. It is my own history I am interested in, IE Denmark-> Germans and Rome.

Really, if you take the Gallic War alone, Caesar does mention the violent warfare between the Aedui and Arverni. This is not a 'hint' at all but a statement of fact.
No it is not, as I have shown above the statement should not be taken at face value, but have source criticism applied to it. I did this in my last post and believe that I exhibited both how one applies S C (the tool of trade of any historian and the only thing distinguishing us from artists and writers of fiction), and that Caesar's statement does not hold up to scrutiny as a statement of fact. If you believed such statements consider that Hitler stated as fact that UK was finished and the war over in 1940. And that Montgomery et al stated as fact that the Germans had only old men and young boys left with which to defend. Find any veteran of Arnhem and ask him about the truth of that statement.
You cannot believe such, for the actual application of Source Criticism to Caesar, see my last post.

In 121 B.C. the Romans defeated, heavily, the Arverni. The power vacuum would have certainly resulted in typical warfare as he Arverni tried to maintain their control of trade and hegemony among the 'lesser' tribes and their allies and dependents. from there the conflict might have started, or it could have achieved impetus much later on. We do not know. We know the Cimbri and Teutone were no friends of the Aedui and Arverni either, but little is said about what went on in Gaul militarily, at this time (one would think that 100,000's of families and people moving through would need food, and the breadbasket was Gaul above all others). But what we do know is these two powers sought supremacy through warfare, and apparently the "many years" of this ongoing war were not going to end anytime soon. Thus Caesar ride in and saves the Gauls from themselves and the Germans.
The crucial thing here is, as you say, We do not know", it is all interpretation and guesswork. And again, you should not take the numbers of the Kêmbroz literally, the numbers given for them in the ancient sources would have comprised an estimated half to third of the population of Germany at this point. Ancient sources always exaggerate enemy nymbers and hide their own losses. In this very thread was mentioned L. C. Sulla's 20-man loss, as an evident example.

If the warfare and losses in Gaul were so bad we would not see a rising urbanisation and trade, quite the opposite. Urbanisation and trade cannot thrive in an environment of strife and violence. Cities are too juicy targets for enemies if there is no strong protection. Now, I do not know much about Gallic history, but I do know that we see an increase in urbanisation and trade. This would be evidence against the dearth of warriors and power vacuum. I also very well know the application of source criticism, I was good at it before I took my degree and it was hammered in further during the years at uni.

So, I persist in saying that we can say nothing of the losses of Gallic warriors on the basis of the sources cited. I also persist especially in saying that Intranetusa is mistaken to claim that Caesar had but to walk in and kick a few old men and starving women and Gaul was his. And lastly I definately persist in claiming that Caivs Ivlivs Caesar deserves praise as one of the great military and political minds of our history.