Questions
1) Can I use pieces of the plants that are left to root the cuttings?
What is the best way to do this? I have rooting hormone and was
thinking about doing this.
2)For plants that have injured leaves, stalks etc, is it better to cut
below the injury and let it regrow from there?
3) How do I keep this from happening again? I am figuring a fence
won't stop a racoon. Are there any smells that deter them?

Answers
1) some plants will root from break offs, eg spearwort, parrots feather, others wont, I dont think marsh marigold or lobellia would. There is probably some logic behind what will and what wont but I dont know it. I would only use rooting hormone on terrestial plants not aquatics. Some aquatics will grow roots even if the bits are floating, I generally shove break offs in a pot with some soil in about 6" of water.
2) not sure about, if the stem was badly kinked then I would probably cut at the kink, I dont know if damaged leave will still feed the root system
3) I think I have seen Coyote?? urine suggested but dont know if it works, what about an electric fence?