OK ... well ... there' s no nice way to put this Robino ... you're screwing it up.
Now please don't get over excited up or upset because I don't mean that in any bad way. But the stuff in the tute does work (it's where I got my first Briefing from) so somewhere along the line you have inadvertantly done something that has stopped it from working. We need to figure out what that is and change it.
It seems to me that the first thing is to get a Briefing - any Briefing - working with your mission. Once we have that, changing it to the Briefing that you want will be relatively easy.
I can't check all the html in your post, mostly because I don't know enough html. However, what I suggest is that you take a Briefing - any Briefing, whether it's the one from the tute, the one from the
Tutorial Mission (a complete working mission designed specifically to help people in your situation) or from an official mission or the user mission of your choice - and get it to work. Don't change a thing, just cut and paste the file and put it in your mission folder next to the mission.sqm and see if that works.
Once it works, you can change it to what you want. Don't touch the code in the first instance, just the text. Do everything one stage at a time. Having no Objectives is an advanced Briefing so don't even think about starting there. Contemplate it only when you have a fully operational ordinary Briefing and you understand how and why it's operational. Learn to walk before you learn to run. (Aside: this is major problem for the OFP communty: far too many people trying to do Evil Kneival stunts before they know which end of the motorbike is the front.)
Make sure your Briefing file is called Briefing.html. If it's called Briefing.html.txt or indeed anything else it won't work.
If it was up to me I'd take all Briefing generators and similar utilities, put them on a big bonfire and burn then until the carbon residue was unrecogniseable. I find them profoundly unhelpful and a highly effective way of preventing people from making missions of an acceptable quality, mostly because the utilities concerned are either of very poor quality to start with or hopelessly out of date,or both. They are particularly unhelpful for noobs because they prevent you from understanding how to make a good mission. However thats just my opinion- lots of people disagree!