If you're getting bummed out about losing 5 subs, then you're in for a rough time ahead. YouTube is a roller-coaster for most people. It's just something you'll have to learn to accept.
You sound a bit bored at first, and the first few minutes is you apologizing for things. Don't worry about the small things, just proceed with confidence . Also, less intro would be good; get into the gameplay as fast as you can.
Yea...you sound pretty bored. I'm personally not a fan of the full game commentary style, and Baumi already has that saturated market for Dota 2. If I were you, I'd try to approach videos more creatively and grab the viewers attention.
Perhaps you should wait until you get questions from your subscribers then? My attitude towards QnAs were always "do them if people are asking a lot of questions", and not to just do one for content creation's sake.
If price isn't an issue, then 1080 is no question a great card. If you want to save a few hundred dollars and lose only a bit of performance, the 1070 and 1060 do fine too, like the previous reply said.
Can we get an idea of what your budget is?
If you're looking for tips, you're posting in the wrong section.
As far as that sponsor goes, you won't find one with 100 subs, or even 1000 without the traffic to back up monetary compensation. You can easily get affiliate codes though.