I'm a beginner and not a good golfer like you seem to be.
You're talking about slicing your irons, right?
I don't know if your problems have been solved by now, however, I have experienced some of the problems you describe.
i.e.: not getting the ball in the air anymore (topping)
In my case, this was caused by the fact that I would stretch-out my knees (move the body upwards) during the back-swing.
the slice might be caused by hitting the ground with the toe of the club first, even if it's just a little bit and you don't even feel it, or maybe you need to keep the toe of the club a little more upright.
I never had a real slice-problem with my irons, but sometimes my shot would go way right with a faint slice, and this was usually caused by putting the ball too much right in my stance and having the club-face a little too much open.
My back-swing is very steep (irons), but never causes me to slice, so I don't believe that's the problem.
Another possibility (happened to me too) is that during your down-swing, you focus too much on hitting the ball to the target, instead of simply completing the horizontal rotation of the upper body.
This could result in hitting the ball way too much in-to-out and causing a slice.
If you haven't solved your problem yet, I hope this helps you.
By the way, Where in Belgium are you from?
I'm from Laakdal, near Tessenderlo.