Changes

I recommend the "Kreuz Oberhausen Holten" to get onto the A3, becoming the A2 direction north towards Hannover and A3 south direction Frankfurt. You have a bridge there to not get your thumb wet in case it rains and people tend to stop for you within the first 15 min.

To get onto the A40 I recommend taking the tram 112 (dir.Muelheim), get out at "Willy - Brandt Schule" and walk back to the entrance of the autobahn. No shelter but a traffic light where people have to stop and notice you.