Learn Spanish (Latin America): ¿Sentirá vergüenza ajena? Es más, ¿estará loco? - Could he be feeling secondhand embarrassment? What's more, could he be crazy?

Es más translates to "what's more" or "in fact." In this lesson's context of argumentative escalation, it takes an initial thought (maybe he feels secondhand embarrassment) and steps it up to a stronger, more extreme guess (actually, maybe he is just crazy). It is the perfect connector for building momentum in your train of thought.

Could I use encima instead of es más here to connect the sentences?

It wouldn't work as well. While both add information, encima (on top of that) usually piles on additional, often annoying facts to a situation. Es más is used to escalate an argument or a real-time thought process, which fits perfectly when you are upgrading a speculative guess from "embarrassed" to "crazy."

Why are sentirá and estará in the future tense if we are wondering about how he feels right now?

This is the "future of probability." In Spanish, you can use the future tense to express a guess, wonder, or conjecture about the present. So, ¿estará loco? is formed in the future tense but is used to mean "I wonder if he is crazy?" or "could he be crazy?" right now.

What is the literal translation of vergüenza ajena?

Vergüenza means "shame" or "embarrassment," and the adjective ajeno (or ajena) means "belonging to someone else." Together, vergüenza ajena is the exact equivalent of "secondhand embarrassment" or "cringe"—the feeling of being embarrassed on behalf of someone else's awkward actions.