If we are to answer the question of whether DCs deserve moral consideration, the first thing we must establish is whether DCs can suffer. If they can suffer then the argument for consideration grows stronger. Sentience often gets conflated with the word intelligence, but at its root it only refers to the ability to suffer. The intelligence of DCs is another question... but I would say that they exhibit sufficient intelligence for us to consider then an intelligence similar to our own.
Bold 1: No. The capacity to suffer pain is a branch of the whole concept, but not the whole tree. If I stripped you of all pain receptors and removed the capacity for emotional pain, you would still be sentient because you can experience stuff like light, sound and other emotions.

Bold 2: Why? How do you know they're not putting on a convincing show?