Bos ya sidi,
You can do everything without a representative, however, your case seems a little complicated and a rep can be much safer lel asaf.. But as long as you don't HIDE info from CIC or lie in your application you should be safe. Some officers are understanding and will demand extra documents and clarification, and some are really cruel and will just reject your whole application. Most rejections are due to missing PCCs and failure to scan all stamps on passports
-Mesh 3ayz afti lol, but where you 'lived' IMO is where you studied or worked, vacations aren't residence places, you can ask about this in a new thread and many members will be able to help.
-LOE is a very useful tool that you can use to support your case, they do look at it and quote it, I had a visa refused in the past and so I answered YES to one statuary question and explained why I got refused in my LOE, the visa officer wrote down on my file that the applicant had a visa refused and its explained in his LOE document number #####, according to my GCMS notes, so I suggest you do use it to your favour. At least it will prove your good intentions, they dislike people who intentionally hide info.
I'm not sure what;s better to use government or private experience but I used the private one, this is were the rep is useful..
They requested military details, so I uploaded shahadet el geish scanned with a certified translation and filled the form they sent me, they asked where I served and mandatory or job service, whether I was in any active combat and why I'm no longer in the military. It prolongs the background check significantly.
-Lol, no idea! get a rep or ask old members here, you'll most probably get all your answers through the forum, start a thread with all your questions and you may not need a rep at all.
Thanks man!

and best of luck.