Go with your gut. That is not a dismissal of your question, it is the most honest answer available.
The feeling you are describing, that quiet persistent sense that something is off, is not paranoia. It is pattern recognition. You have been watching this person, talking to him, reading his words, and your instincts have been collecting data the entire time even when your conscious mind was choosing to trust. When that internal alarm goes off, it is worth taking seriously.
A tattoo of your name is a gesture, and gestures cost less than people think. Getting a name tattooed in prison is not particularly difficult or expensive, and it is a powerful signal to send to someone on the outside who is deciding whether to keep investing time, money, and loyalty. It costs him very little and buys a great deal of reassurance from you. The same logic applies to marriage in certain circumstances. It is not that those things are meaningless, it is that they can be meaningful and still be strategic at the same time.
The more useful questions to sit with are behavioral ones. Does he ask about your life or only talk about his situation? Does he express concern for your wellbeing or primarily make requests? Does the conversation shift when you mention financial stress or pull back on support? Does he become more attentive right before he needs something?
Those patterns tell you more than any single gesture does.
You already know something is wrong. The courage required is not in figuring out whether you are right. It is in deciding what you are going to do once you accept that you probably are.
Trust yourself.