He hasn't done anything to hurt Pip - yet
He sort of has, by lying to Rex about the circumstances in which they got together. Rex could well react quite badly to that and it could have put an end to their friendship.
The debacle with the chutney was an honest mistake, and one made as a result of Pip and Toby helping Jill. Indeed I'm not convinced that it was actually Toby's fault. Both Pip and Toby owned up to it (which was rather sweet).
Yes and no. It wasn't deliberate, but it was a product of Toby being a careless twat who can't be bothered to think things through, and who didn't care how much trouble he could cause if he got it wrong. He was probably inwardly sneering at the local yokels and thought that the task was so far beneath him that he needn't expend any thought on it. It was pretty obvious that when Pip owned up to it she was doing so in order to save Toby, and Toby was the only person responsible for the mistake.
If the flower and produce was so important to Jill then she should have checked that the jars had been set out properly.
The issue for Jill was that the mistake directly put her into an extremely embarrassing situation. She had no reason to expect that to happen, so no reason to try to anticipate it and guard against it.