I think that some of your points are valid (short staffing of tills needs to be fed back, asking them to check the temperature, why there was an inconsistency with the food service provision)... but...
if you did genuinely email it in that format, it's horridly presented, and a very weak complaint letter.
In future, you should bullet point your concerns. "I am concerned about X, because of Y. Example given."
You should also make a clear case for what you want done. A random suggestion to send them onto a training course isn't practical - I'm sure they've already been. A time limit for a response would also have been helpful e.g. "I look forward to a satisfactory response within 10 working days, and will seek to escalate this to ABC party (CEO? Whatver) if this is not forthcoming."
In other words - whilst you have a few general complaints to feed back to them, which may be valid, the execution is terrible. It's the sort of thing I'd expect my 14 year old DSto write if he was unhappy with a company. Sorry.
There are a lot of complaint letter templates on the internet, I assume, I'd suggest next time you make use of them. I also wouldn't hesitate to write information about if you've been a regular customer etc (as long as it's true) - personally when I write complaint letters it's only because I'd prefer to use their services again. And the response to the complaint letter determines if they are added to my mental boycott list, or get a 2nd chance. Adding in information about it being "your local cinema" or the one nearest to their school, etc., I think frames a complaint better.
Just my opinion though!