I think that’s supposed to be a dragon tattoo on that guy’s right arm.
Your right arm is your right arm.
The reading can either be a combination of the kun'yomi readings (more common) or the on'yomi readings (pretty uncommon, and only used to talk about sports players, especially baseball). That being said, you've seen all of these readings except う. Here's a mnemonic for if you want to remember う: Your right arm got pricked by a poisonous uni (うに), and it has to be amputated. Hope you're not right-handed!