Avira,
I didn’t say the RambaM was clear, I said the RambaN was clear. He says it in multiple places. And it is not just him. Most Rishonim hold that hashgacha pratis is limited in some way, either just to tzadikim, just to humans, or just to humans.
Your Gemara in Chulin is a good raya. I will need to look up how the Ramban and other rishonim that hold that hashgacha pratis is limited to tzadikim explain that Gemara.
Your raya from the Rambam in Hilchos Taanis is not a good raya. The Rambam is discussing the tzibur. When bad things happen to a tzibur, that is always hashgacha–at least hashgacha klalis.
I don’t think going by what you were taught as a child is a good measure of Toras Emes. Part of the mesorah is that you grow up and learn seforim inside and understand the nuances and machlokesim. No amount of sifrei kabalah or chasidus can override rov Rishonim. Moreover, the Ramban learned kabbalah and still wrote what he wrote.
I don’t think your explanation of Rav Elyashiv’s position is accurate. Of course a person can rely on Rishonim–especially for hashkafah. Slifkin didn’t have any Rishonim supporting the parts of his views that got his books banned. He had some Rishonim who said superficially similar things in different circumstances. The fact that Rishon says that Chazal could make a mistake (something that is obviously true because they are human), doesn’t give Slifkin grounds to say that they made a bunch of mistakes on specific issues.
We aren’t dealing with obscure Rishonim, or texts that were found recently in this case. These are amudei oilam, meorei hagolah. The mesorah, rests upon the shoulders of the Ramban and the Rambam. You can’t mach avek with them because it doesn’t fit with the Nefesh HaChaim or the Baal Shem Tov.