I had been through this before. I had to separate the cats. You might have to find another place a liter box for bennie. Ours got so bad, we had to get rid of the trouble maker. She might have been abandoned due to her behavior or the hormones of being pregnant might have left her an unfriendly...
The grass your cat is eating could have pesticides on it. Vet is a choice, I understand about budgets. I have grown my own grass before too.
Some cats, though they might like their walks, might not be good with them. Don't stop your walk to let him eat the grass for a week. If he stops...
