I just replaced all rail etc.. on my 88 190e. I know they are very different cars but, what i did to remove my crank bolt, was I stuck a wooden handle of a hammer into the flywheel area to keep it from spinning, then I had my breaker bar on the socket which was over the crank bolt. That wasnt cuttin it, so i put a 3.5 foot peice of copper pipe over the breaker bar, and WOW the bolt started moving. I was pretty impressed on how well this pipe worked for me. So give that a try. If you have room to get an impact wrench in there then give that a try. I couldnt fit the impact wrench between my a/c condensor(?) and the bolt.
On my 4 clyinder this was a pretty big job, I had more bolts off then when i swapped out engines.
1988 190e 2.3 with 91 engine