How can I keep Gandhi satisfied? (He's a Peacekeeper and Nuke Happy )
I would recommend being a peace maker. Build a few nukes but don't use them.
By the way, these traits of Ghandi aren't particularly meant to work together well, but are tribute to a bug: Why Ghandi is such an asshole in Civilization and Gandhi is still an asshole in Civilization VI.
If you don't like his nuke trait, you could remove it with a mod.