Your whole theory is based on this language argument. I assume you live in America. Look around you. There are descendants from Italy that don't speak a lick of Italian, Japanese-Americans that don't speak any Japanese, etc. It only takes two generations to adopt the language of the majority. As the tribes moves across Europe, they would've had to speak the languages of the surrounding peoples. Just because the British don't speak pure Hebrew doesn't mean anything. Your argument is dumb.
Who has based their arguments on the fact that English isn't identical to Hebrew? I've seen that nowhere on this thread.
Interestingly, I addressed Italian and Japanese progeny living in America at #343. To say that they don't speak a lick of their ancestral tongues isn't accurate. Sushi and spaghetti are preserved, as are other words. Not only that, they've entered the common parlance of American English, despite vastly more methodic and comprehensive forces for assimilation. Linguists of the future will be able to infer interaction between America and both Japan and Italy from these relic words.
Where are the corresponding relic words from which we can infer any interaction between the Celts and the Lost Tribes?
Maybe they exist, but I'm still waiting for evidence of them.
If they aren't being absorbed, if they're not subjugated, if they're in a large group, they keep their language. See, for example, the Romany Languages.