"Have a good day" comes to mind or "I m really busy right now, ttyl" or not responding at all if you don't feel like it come to mind too.
He is starting to panic (and act up) because he feels his grip on you slipping.
Great job on your sister too
You have a right to not engage (or disengage) with people's toxic bs no matter how close they are to you.
but I do have a question - why did you give him a lovey card if you are feeling "anti"? Are you "trying" - I don't know your whole story but I couldn't put my head around the card and the rest of the story...
I agree with that, don't give lovey cards unless you mean it. People pleasing can really trip you up (I have a tendency to people please myself believe it or not..always have to watch out for it).