I think you are right. I think they are both bewildered by their own depravity and loss. I think Ludwig expects the death penalty. This was a case of suicide by murder.
Yes, it seems the 'run away and start a new life' was kind of an afterthought, a panic to their actions. I'm not sure the reality of what they've done, since they fled immediately, has really sunk in for them. Or has it and they are simply filled with that much hate toward her parents? Ironically, had they bothered to think it through, they might have gathered up cash and simply run away together as many have tried and some succeeded, without murdering anyone.
I think Ludwig expects the death penalty. This was a case of suicide by murder.
I think you're right, too. He does seem remarkably calm and nonplussed by his actions. So much for the new life with his girlfriend. I think you've hit it, suicide courtesy of the state.