Fair enough - but I'll only do one as I'm short on time. Corrections in square brackets
'sittinginthemorningsun Chelsy we're chatting casually on an internet forum, not taking an A level paper
[full stop at the end of a quotation needed here]
Alas, when you receive a letter from the NHS or your local authority containing spelling errors, it does make you doubt their ability to get other things right.
[If I were being a stickler, I'd quibble the punctuation, but it's colloquially acceptable.]
I was thinking more of posts on Facebook though.
[Comma after 'Facebook' needed, and 'however' would be better English.]
Am I the only person to have FB friends (not all with degrees) who post in better English in their second language than quite a considerable number of native English speakers?
[This is badly phrased - your 'better than' needs to be comparing like with like. You've meandered from comparing languages ('better English') to comparing people ('English speakers').]
I have several friends from a country where there is no universal free education
[comma would be good here]
and its
[it is, or it's - you need an apostrophe when you contract]
only available to those whose parents can pay or who benefit from charity, and even then commonly not as long as the English receive.
[receive it? I think you've missed out a word here]
Hope that was actually useful - I would never correct to this level for someone who wasn't happy to be corrected, and some of these, as you can see, are more quibbly than others.