If you could help me with this I would appreciate it. I really don't know what I am looking for and I do not understand the compounds well enough. I mean I don't even know how to actually blanch them or what should be blanchedSo, there's a very good chance nothing bad comes from this and he recovers. I'd think optimistically for now and just do what you can(see a vet, change gutload, etc).
You could also try blanching or even cooking the veggies to remove some of the negative nutrients. Dandelion greens are great, but I believe they have a moderate amount of oxalates, I'd have to check up on that again.