The information of Thorwald being a german and dutch variant is correct.
I don't exactely know what (language) you mean when you say Germans have problems distinguishing between w and v?
"valdr" is the Old Norse equivalent to german "walten", so that's where the w comes in.
My Personal Name Lists, feel free to vote!
Female:
https://www.behindthename.com/pnl/139318/112909Male:
https://www.behindthename.com/pnl/139318/112910