Since the Jandd Disc adapters are design to be on the lower eyelet of a rack, they should be plenty strong to handle the type of load they experience at the seat stay. Personally I would have cut off the lower legs of the Wald so they would mount to the eyelet and not get in the way of the skewer, but functionally there's probably not a ton of difference, as it looks like by removing the skewer you can still drop the wheel out normally. You'd probably need a tandem length skewer to clear as it is.

The brake doesn't look like a huge deal, if it's not causing any rubbing. You may be able to get it to route under the Wald arms by trying a longer piece of housing, or maybe route in the other side of the seatpost with a more bendy noodle and housing.

I don't think you've lost any ultimate capacity by having it mounted off level. I would however try to load the heaviest items towards the front and lighter items reward, as I've had problems with an overly rear biased load causing the front to get rather light and squirrely.