The "él" should have an accent, in this case it is quite important because it should be the personal pronoun "él" and not the article "el". Then: "Tú y él lo hacéis todo mejor". I think this means that "You and him (both) make everything better". The phrase in Spanish is a bit ambiguous: I think it could be interpreted as "You and him make DO everything better (than me/someone else)" or "You and him make everything better" as in "You make everything feel/be better". Hope this helps :)

I'd translate "Tú y él lo hacéis todo mejor" to "You and him make it all better". I do think it emphasizes the same way "all" does in English. Somehow this phrase could also mean, in a very specific situation, that you and him are better than me/someone else at everything.