Possible, yes, it wouldn’t be a very clean reaction due to competition with other pathways. One would obtain a lot of elimination and rearrangement through E1 pathways.

It has a full “formal charge”, but formal charge is not always a helpful gauge of electron density. Compare the electronegativities of O and H, and that will tell you where the electron density is. See this post: Watch Out, Formal Charge Can Mislead: https://www.masterorganicchemistry.com/2012/02/22/common-mistakes-formal-charges-can-mislead/

? This post doesn’t address alkyl halides. It addresses formation of ethers from alcohols. Can you be more specific?

The reaction here is one where there are very few possible side reactions. A single reactant, and the electrophile only differs from the nucleophile in being its conjugate acid. A primary electrophile, with no chance of ionizing to a carbocation, no chance of rearrangement, and the only side-product is elimination. So it’s kind of a special case.

I actually suggest you don’t use this method, unless you are trying to make diethyl ether on industrial scale. Use anything else. You can thank me later.