Pain in the English

My local Public transport company has started delivering recorded messages on the train platform “Please be advised that patrons must wait till the train has come to a complete stop before crossing the yellow line”. I find this message completely grates on me, and I suffer it each time I wait on the train platform for my train.

“Please” is a polite request for me to take some form of action. I have a choice. I can comply with the request or I can refuse the request.

If an instruction is given to me with the precursor “Please be advised” then I am presented with a fait accompli and have no opportunity to decide whether I will comply with the request or not. It is not, in fact, a request in any form and does not provide the recipient with any capacity to dismiss or refuse the request. For this reason, I consider it to be manglish.

Can you confirm that “Please be advised” is manglish?

Is it correct to say “Let's you and I” or “Let's you and me”?

Why is it more appropriate to say the big, red bull was running fast, rather than the red, big bull was running fast?

I'm wondering about the phrase, “try and.” (Used like this: “I'm going to try and stop him.”)

I know that it's technically grammatically correct, but is it okay to say it? Would it be better to say, “I'm going to try TO stop him” instead?

I've heard people say “as it were” quite often. It doesn't even sound wrong to me anymore. But shouldn't it really be “as it WAS” instead, for proper subject verb agreement?

Where does that phrase come from and what does it mean?

I know the saying was popularized from the movie Alice in Wonderland. Did the expression “off with their heads” have it's origin in England or France?

As nasty as it sounds, for a translation I just need to know what the word is for the shooting into head of an executed person after being shot by the fire squad. Is it a head shot? Or there is a military jargon for it?

When I lived in Canada (I'm Australian) I noticed a common phrase used by interviewers and reporters was “could you speak to that” used in the sense of “Prime minister I believe you have discussed changes to the immigration policy… could you speak to that?” I found it a little uncomfortable and wondered if it was a new journalistic lingo phrase or a perfectly correct Canadian expression.
Could any Canadians speak to that? : )

What does “tooing and frowing” mean? And why these words cannot be found in any dictionary (at least in those I looked at?) Is it a corruption of “to and fro?”
Is “frowing” a word and could it be used separately and if so would it mean differently than that of the phrase?