marmot, stats are irrelevant and trust me when i tell you that if you guide your gameplay according to them you're only gimping yourself. The current stats system is based on KpD which is not a measure of skill in tf2. I could give you a ton of examples why that's true but I cba writing so much. I'll just say that it favoures some classes to others.
So just give up on them alltogether.

I know that stats aren't showing the real skill, but that's annoying, that you are having top places in team, and your stats are going down and down ;D .

Simple example, it's impossible to lose ranking points while playing medic.

this is true and it's the only reason my ranks anywhere near as low as it is

one thing about the stats, would it be possible to implement a record of points:death as opposed to kills:death? because that would be more useful and representative.

That is already currently the case. You recieve skill points for all non-kill events which gives you points on the scoreboard as well.

You could play heavy and mod the sandvich skin to be a hamburger

Or better yet, he could play heavy and mod arrows to look like hamburgers and I'd hand the hamburgers to him on a daily basis

You could play heavy and mod the sandvich skin to be a hamburger