If you read a lot it's pretty easy to recognize the correct spelling.

Same. I may not be able to verbally spell them, but I can see the "right" one.

Same.

I was born & raised in the US, and it wasn't till I was working in my 20's that someone told me that it is height all the time, not heighth. I assumed it was like width & depth.

wright = person who works things. hence , wr in work and in wright. A bit like Fear/Fright.

same.

Q2, third option is Jewellery, spelt correctly.

"he's nauseous" versus "it's nauseating"

No.

Technically, yes. The traditional dictionary definition of "nauseous" is "causing nausea," not "experiencing nausea." In current practice, however, they tend to be used interchangeably. Something that makes people feel nausea could be described as either nauseous or nauseating; someone experiencing nausea could be described as either nauseated or nauseous (with the older, technically correct term first and the modern, de facto synonym second, respectively).

“It” is an exception to the usual rule, just to make English even more confusing.“Its” is used for possession to differentiate it from “it’s”, which is a contraction of “it is”. I hope that makes sense!

Mid sentence

When NOT has just occurred mid-sentence ....

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Yes they are in UK English!